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AN INTRODUCTION TO ORACLE AND SQL

1. INTRODUCTION

ORACLE is a Relational Database Management System (RDBMS). As such, the only data

structure that it supports is the TABLE. A Table is simply a two-dimensional matrix with

horizontal ROWS and vertical COLUMNS. Readers may be interested to note that a RDBMS is

an implementation of Codds Relational Data Model and that in the literature on relational

topics certain items are often slightly different. In particular, our Tables are called RELATIONS,

our rows are called TUPLES and our columns are called ATTRIBUTES.

ORACLE has one language to handle both definition and manipulation of the data.

Furthermore, this same language also deals with Security aspects.

This language is called SQL ( Often referred to as SeQueL or Structured Query Language).

Although the trend is to provide the user of ORACLE applications with higher level user-

interfaces (e.g. Forms based application screens) where no knowledge of SQL is necessary, it is

essential that anyone involved in the development of ORACLE applications has a thorough

grounding in SQL.

People registered as ORACLE users will obviously wish to create and manipulate their own

Tables. However, the approach taken by this introductory text will be to concentrate initially

on the retrieval aspects of SQL. In particular, we will consider retrieval operations on some

sample tables to which all users have been granted read-only access. The sample tables are

EMP, DEPT, SALGRADE are described in Appendix 1.

Readers wishing to define and manipulate their own tables are advised to read Chapters 7 and

8.

This introductory text should be used as a manual and therefore you should not attempt towork through it in sequence. An initial read through is recommended so that you get an idea

of the range of features available, after that use the manual for reference purposes only.

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2. GETTING STARTED WITH SQLPLUS

2.1 SQLPLUS

ORACLE RDBMS has a number of component software parts. The component that we shall

use to familiarise ourselves with SQL is called SQLPLUS.

SQLPLUS consists of the usual SQL data manipulation, definition and access statements, plus

a number of extra statements for formatting, report-writing and file-handling.

SQLPLUS statements are held in an SQL buffer. The current line operated on by the keyboard

is known as the Command Line, but an SQL statement may spread over several lines.

2.2 Using SQLPLUS Graphical User Interface

To start the graphical user interface:

Choose Start> Programs > Oracle for Windows NT > SQL Plus 8.0The Log On dialog box appears:

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1. Enter your user name and password (given to you in class). In the Host string part enter

eden01.

2. Click OK.

The Oracle SQLPLUS application window is displayed.

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2.2.1 Using the SQLPLUS Application Window

SQLPLUS displays the SQL command prompt in the application window. To enter SQLPLUS

commands, type each command at the SQL prompt and press Enter.

You can use the mouse buttons to copy previously entered SQL commands to the current SQL

prompt.

To copy a command, highlight the intended command with the left mouse button. While still

holding down the left mouse button, click the right mouse button. SQLPLUS copies the text to

the SQL prompt.

2.2.2 Using the SQLPLUS Menus

This section describes the menus in the GUI version of SQLPLUS.

File Menu

The File Menu contains the following commands:

Open The Open command retrieves a previously stored command file.

By default, SQLPLUS looks for a command file with the .SQL extension.

Save The Save command contains three subcommands:

Save Create, Save Replace and Save Append.

Save Create saves the contents of the SQLPLUS buffer in a command file.

Save Replace replaces the contents of an existing file with the contents of the

SQLPLUS buffer. If the file does not exist, SQLPLUS creates the file.

Save Append adds the contents of the SQLPLUS buffer to the end of the file

you specify.

After you save a command file, you can do the following:

Retrieve the file with the Open command from the File menu.

Edit the file with the Editor command from the Edit menu.

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WHERE JOB MANAGER;

e.g. SELECT * selects ALL rows from the EMP table where the

FROM EMP job is MANAGER or CLERK.

WHERE JOB = MANAGER

OR JOB = CLERK;

e.g. SELECT * selects ALL rows from the EMP table where the

FROM EMP job is not MANAGER or CLERK.

WHERE NOT (JOB = MANAGER

OR JOB = CLERK);

Note that the WHERE clause causes a Horizontal 'slicing' of a Table.

3.3 Boolean Operator definition and Precedence

Operator Meaning

= equal to

(or !=) not equal to

> greater than

>= greater than or equal to

< less than


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a) AND - OR precedence

WHERE SAL> 1500 AND JOB = MANAGER OR SAL > 1200 AND JOB = SALESMAN

^ ^ ^ ^

condition 1 condition 2 condition 3 condition 4

The expression will be carried out as follows:-

1. Each of the 4 conditions are evaluated to be true or false

2. Condition 1 and Condition 2 are ANDed to produce TRUE if both are true and FALSE

otherwise

3. Condition 3 and Condition 4 are ANDed to produce TRUE if both are true and FALSEotherwise

4. The results for 2. and 3. are ORed together to produce a final result of TRUE if either is true

and FALSE otherwise.

b) BETWEEN

SELECT * This is equivalent to WHERE SAL >= 1200

FROM EMP AND SAL 1400

WHERE SAL NOT BETWEEN 1200 AND 1400;

c) IN

SELECT *

FROM EMP

WHERE JOB IN (CLERK, ANALYST, SALESMAN);

Selects rows where the JOB is CLERK, ANALYST or SALESMAN

SELECT *

FROM EMP

WHERE JOB NOT IN (CLERK, ANALYST, SALESMAN);

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Selects rows where the JOB is not CLERK, ANALYST or SALESMAN

d) LIKE

LIKE is used to match character patterns, and in order to do this, recognises two special

characters in a character value:

% represents any sequence of zero or more characters

_ represents any single character

SELECT *

FROM EMP

WHERE ENAME LIKE M%;

Selects rows where the ENAME column begins with M.

SELECT *

FROM EMP

WHERE ENAME LIKE ALL_N;

Selects rows where the ENAME column consists of ALL (any character) N

e.g. ENAME has the value ALLAN, ALLEN, ALLZN

The characters % and _ can be used in any combination in a character pattern.

e) IS NULL

Sometimes, values for a column are not known, or are inappropriate. In a case like this, the

existence of a NULL value can be entered. Note that NULL is not the same as zero.

SELECT *FROM EMP

WHERE COMM IS NULL;

Selects rows where the commission field has no entered value, except for the value NULL.

3.4 Ordering Rows

When rows are selected from a table or tables, the order of their display is undefined. In fact,

the order may be different for the same query at a different time. If a particular order is

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required, then an ORDER phrase must be added to the query. The ORDER appears after any

WHERE phrase.

e.g. SELECT *

FROM EMPORDER BY EMPNO;

Orders all the rows of the EMP in ascending order of EMPNO. Ascending order is the default.

e.g. SELECT *

FROM EMP

WHERE DEPTNO = 30

ORDER BY SAL DESC;

Selects all rows where the DEPTNO is 30 and orders the output in descending order of SAL.

e.g. SELECT *

FROM EMP

ORDER BY JOB, SAL DESC;

Orders the EMP table firstly in alphabetic order of JOB and then for each JOB by descending

order of SAL.

Note that if there are NULL values in an ORDER BY column, then they will appear first,

regardless of whether the required order is ascending or descending.

3.5 Selecting Columns

As well as making horizontal operations on a table through selection of rows, it is possible to

make vertical operations on a table by selecting some subset of the Columns or even by

embellishing the table with extra columns produced by Functions acting on existing columns.

e.g. SELECT EMPNO, ENAME, SAL

FROM EMP;

Selects only the EMPNO, ENAME and SAL columns;

e.g. SELECT EMPNO, ENAME, SAL

FROM EMP

WHERE DEPTNO = 30;

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Selects only the EMPNO, ENAME and SAL columns from those rows where the DEPTNO is

30.

3.5.1 Eliminating Column Duplicates

Sometimes when certain columns are selected, Duplicate values appear:

SELECT JOBFROM EMP;

If it is required that duplicates are not to be repeated, then the DISTINCT option will eliminate

them.

e.g. SELECT DISTINCT JOB

FROM EMP;

3.5.2 Creating Column Aliases

When queries are displayed, ORACLE normally uses the column names that have been defined

in the table. However, it is possible to rename the column if desired.

e.g. SELECT EMPNO, ENAME EMPLOYEE_NAME,

SAL SALARYFROM EMP;

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This leaves EMPNO with the same name but renames ENAME as EMPLOYEE_NAME and

SAL as SALARY.

Note that column names can be specified in any order - even an order different to the definedorder in the table. Displayed results will be in the order defined in the QUERY.

4. JOINING TABLES

4.1 Introduction

In the Relational approach to data, rows in different tables are related by having identical

values in certain columns of the tables. For example, rows in the EMP table with DEPTNO =

30 are related to the row in the DEPTNO table with DEPTNO = 30. The technique of relating

different tables is called JOINING.

e.g. SELECT *

FROM EMP, DEPT

WHERE EMP.DEPTNO = DEPT.DEPTNO;

The WHERE clause is responsible for the JOIN. The result is a table with all the columns of

both original tables.

Note that in order to avoid confusion between the DEPTNO column of the EMP table and the

DEPTNO column of the DEPT table we qualify the appropriate DEPTNO by putting the name

of the owning table and a full-stop (.) at the front. e.g., EMP.DEPTNO.

e.g. SELECT *

FROM EMP, DEPT

WHERE SAL > 1000

AND EMP.DEPTNO = DEPT.DEPTNO;

This joins the EMP and DEPT tables as before, but also selects only the rows where the SAL

value is greater than 1000. Note that the order of the two WHERE conditions is irrelevant.

e.g. SELECT ENAME, DNAME

FROM EMP, DEPT

WHERE SAL > 1000

AND EMP.DEPTNO = DEPT.DEPTNO;

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This is the same as the previous query except that only the ENAME and DNAME columns are

chosen.e.g. SELECT ENAME, DNAME

FROM EMP, DEPT

WHERE SAL > 1000AND EMP.DEPTNO = DEPT.DEPTNO

ORDER BY ENAME;

This query is the same as the previous one except that the rows are displayed in ascending

order of ENAME.

4.2 Types of Join

All the examples of the previous section are of the join type known as the EQUI-JOIN. This isbecause the connecting of the tables is based on values in the tables being EQUAL. However,

other types of join exist which connect tables on the basis of values in the tables having

relationships other than equality.

e.g. SELECT X.ENAME, X.SAL, X.JOB, Y.ENAME, Y.SAL, Y.JOB

FROM EMP X, EMP Y

WHERE X.SAL > Y.SAL

AND Y.ENAME = JONES;

This query is designed to find the salaries and jobs of employees who earn more than JONES.

It is quite complex and invokes a number of new concepts. Its main point is to define a

sensible query involving a join which is not an Equi-join. In this case we have a GREATER-

THAN join (i.e. X.SAL > Y.SAL).

Another idea here is the concept of joining a table with itself - i.e. the EMP table with itself.

The way that is done is to form two distinct copies of EMP which are called X and Y in thisexample. The definition of the copies is achieved via the FROM EMP X, EMP Y statement.

Note that we can qualify the column names in the SELECT phrase, i.e. X.ENAME, X.SAL,

Y.ENAME. Joins can be defined for other operators, e.g. =,!= etc.

Outer Joins

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The above examples are of the type known as INNER-JOINS. In an inner-join, if a row in one

of the joining tables does not satisfy the condition, it will not appear in the result. e.g., in the

EMP table there is no employee with a DEPTNO of 40. This means that the result of

SELECT DEPT.DEPTNO, DNAME, JOB, ENAMEFROM DEPT,EMP

WHERE DEPT.DEPTNO=EMP.DEPTNO

AND (DEPT.DEPTNO = 30 OR DEPT.DEPTNO = 40);

would only contain a row with DEPTNO = 30. We might, however, want to record the fact that

DEPTNO = 40 is the number of the OPERATIONS department. In order to include a row with

DEPTNO = 40 we must use an outer join. This is denoted by the (+) symbol. The query then

becomes:

SELECT DEPT.DEPTNO, DNAME, JOB, ENAMEFROM DEPT,EMP

WHERE DEPT.DEPTNO=EMP.DEPTNO (+)

AND (DEPT.DEPTNO = 30 OR DEPT.DEPTNO = 40);

Note that the EMP.DEPTNO is the term with the (+) sign. This indicates that the EMP table is

the one that might not have a DEPTNO value.

5. HANDLING DATA TYPES

ORACLE supports Number, Character, Date and Null data types. The following sections

describe how the data types are handled.

5.1 Handling Numbers

5.1.1 Displaying Numbers

Number values are normally displayed with as many digits as necessary for accuracy up to thestandard width of 10 digits. The standard format can be altered by use of a FORMAT model in

a COLUMN command. The structure of a COLUMN command is:

COLUMN column-name FORMAT format-model;

Some format-models are:-

FORMAT VALUE DISPLAYS AS EXPLANATION

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You may use arithmetic expressions in the condition of a WHERE clause.

e.g. SELECT ENAME, SAL, COMM

FROM EMP

WHERE COMM > 0.25 * SAL;

Lists employees whose Commission is greater than 25% of their Salary.

You may use arithmetic expressions in ORDER BY clauses.

e.g. SELECT ENAME, SAL, COMM, SAL+COMM

FROM EMP

ORDER BY SAL+COMM DESC;

Arithmetic expressions can be complex, i.e. with several operators.

5.1.3 Special Arithmetic Expressions

SQL has a number of special arithmetic expressions.

FUNCTION EXAMPLE RESULT

ABS ABS(BALANCE) Absolute value of BALANCEGREATEST GREATEST(SAL,COMM) Largest value of SAL and COMM

LEAST LEAST(SAL,COMM) Smallest value of SAL and COMM

ROUND ROUND(SAL,2) SAL rounded to 2 digits after

decimal point

TO_NUMBER TO_NUMBER(GRADEPT) Converts a CHAR value

containing a number to a number

value

TRUNC TRUNC(SAL,2) SAL truncated to 2 digits after

the decimal point

Some examples are now shown which illustrate the use of some of the above functions.

e.g. SELECT ENAME, GREATEST (SAL,COMM)

FROM EMP;

For each employee, the name and value of Salary or Commission, whichever is the greater, is

displayed.

e.g. SELECT ENAME, SAL, SAL/22, TRUNC(SAL/22,0), TRUNC(SAL/22,2)FROM EMP

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WHERE DEPTNO = 30;

For the Department with DEPTNO = 30 the employee name and various truncated displays of

the Salary are shown. The division by 22 is because the daily salary is being calculated and it

is assumed that there are 22 working days in the month.

e.g. SELECT ENAME, SAL, SAL/22, ROUND (SAL/22,0), ROUND(SAL/22,2)

FROM EMP

WHERE DEPTNO = 30;

This is the same as the previous query, except that some Rounded display formats are shown.

5.1.4 Group Functions

The Arithmetic Functions of the previous section are operating on EACH row of a query.

However, sometimes we might want to obtain information about GROUPS of rows. e.g.,

maximum salary for each JOB or the average COMMISSION of SALESMEN. In order to

achieve this, SQL provides GROUP functions


AVG AVG(SAL) Average value of SAL

COUNT COUNT(COMM) Number of non NULL values in

the COMM column

MAX MAX(SAL) Highest value of SAL

MIN MIN(SAL) Lowest value of SAL

SUM SUM(COMM) Sum of values of COMM

e.g. SELECT SUM(SAL),SUM (COMM)FROM EMP

WHERE JOB=SALESMAN;

Finds the total salary and total commission of salespeople.

e.g. SELECT 12* AVG(SAL+COMM)

FROM EMP

WHERE JOB=SALESMAN;

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Finds the average Annual salary, plus commission of all salespeople.

e.g. SELECT MAX(SAL),MIN(SAL),MAX(SAL)-MIN(SAL)

FROM EMP;

Finds the highest and lowest salaries (of all employees) and the difference between them.

e.g. SELECT COUNT(COMM)

FROM EMP;

Finds the number of non-null commissions.

e.g. SELECT COUNT(DISTINCT JOB)

FROM EMP

WHERE DEPTNO = 30;

Finds the number of DIFFERENT jobs held by the employees of department 30. The

DISTINCT phrase eliminates duplicates before the count is made.

e.g. SELECT COUNT(*)

FROM EMP

WHERE DEPTNO = 30;

Counts the number of employees in department 30. Count(*) counts all the rows satisfying the

WHERE clause.e.g. SELECT ENAME, JOB, SAL

FROM EMP

WHERE SAL =

(SELECT MAX(SAL)

FROM EMP);

This is a special type of query. The SELECT clause in the brackets is a SUBQUERY. Subqueries

will be dealt with in more detail in Chapter 6. The subquery SELECT returns a single value,

namely the largest value in the SAL column of EMP. The query them becomes find the name,

job and salary of the employee(s) whose salary is equal to the largest salary.

5.1.5 The GROUP BY phrase

Sometimes we might want to find out information about several groups within a table. e.g., we

might want to find the average salary for each job. This could be achieved by:

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e.g. SELECT DEPTNO

FROM EMP

WHERE JOB = CLERK

GROUP BY DEPTNOHAVING COUNT(*) >= 2;

Lists all the departments with at least two clerks.

If you want to give a computed column a label other than the original expression, it can be

done in the same way as for uncomputed columns.

e.g. SELECT JOB, AVG(SAL) AVERAGE_SALARY

FROM EMP

GROUP BY JOB;

Renames the AVG(SAL) as AVERAGE_SALARY. If two separate words are required then

replace the AVERAGE_SALARY with AVERAGE SALARY. The quotes ensure that the two

words are displayed together.

5.2 Handling CHAR values

Columns of the Character data type can be redefined using the COLUMN statement, which, as

before, has the structure:

COLUMN FORMAT format-model;

The format model this time is merely A followed by the number of characters, e.g. A25.

Once set, a column format will stay in effect until you redefine it or exit from SQLPLUS.

A column format can be reset by using COLUMN column-name CLEAR.

5.2.1 Concatenation

The only operation that can be carried out on char fields is CONCATENATION. This is where

two or more fields are joined together. The CONCATENATION operator is | |.

e.g. SELECT DNAME | | - | | LOC DEPARTMENTS

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FROM DEPT;

This results in:

DEPARTMENTSACCOUNTING - NEW YORK

RESEARCH - DALLAS

SALES - CHICAGO

OPERATIONS - BOSTON

i.e., the value in the DNAME field is concatenated to blank space, minus sign, blank space

concatenated to the value in the LOC field and the new column thus formed is called

DEPARTMENTS.

5.2.2 An Apostrophe in a char constant

Since an apostrophe is used to denote a char constant, e.g. fred, if you want to denote an

apostrophe in the middle of a char constant, you must in fact use two apostrophes. e.g. in

order to denote freds, you must use freds.

5.2.3 Char Functions

Some common char functions are:-FUNCTION EXAMPLE RESULT

DECODE DECODE(GRADE, A,4,B,3, Translates letter grades in

C,2,D,1,0) the GRADE column into

grade points

INITCAP INITCAP(ENAME) Capitalises the first letter

of each word

INSTR INSTR(LOC, ) Returns the position of

the first blank space in

the location

LENGTH LENGTH(ENAME) Length of the employees

name in characters

LOWER LOWER(ENAME) Converts an employees

name to lowercase

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Displays the word EMPLOYEE as the first column of each row. The column has no heading.

5.3 Handling Date Values

5.3.1 Standard and Alternate Date Formats

The default or Standard date format is like 12-JAN-85. This format is written:

DD-MON-YY.

You can convert the date to a different format using the TO_CHAR function. The structure of

the function is:

TO-CHAR(date-value, format-model)

Thus, to convert from 12-JAN-85 to 01/12/83 you would use the function

TO_CHAR(HIREDATE,MM/DD/YY) where it is assumed that the original date is held in

HIREDATE.

There are other possible date formats, as follows:

DD.MM.YYYYMONTH DD,YYYY

DY DD MON YY

Some common formats are:

ELEMENT MEANING

YYYY or SYYYY YEAR; S prefixes BC date with sign (-)

YYY YY or Y Last 3,2 or1 digits ofYEAR

SYEAR or YEAR YEAR, spelled out;S prefixes BC date with (-)

BC or AD BC/AD indicator

B.C. or A.D. BC/AD indicator with full stops

Q Quarter of year

MM Month

MONTH or MON Name of month or three letter abbreviation

DDD DD OR D Day of year, month or week

DAY or DY Name of day or three letter abbreviation

AM or PM Meridian indicator

A.M. or P.M. Meridian indicator with full stops

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HH or HH12 Hour of day (1-12)

HH24 Hour of day (0-23)

MI Minute

SS Second

/ . , etc Punctuation is reproduced in the result

... Quoted string is reproduced in the result

The suffixes below may be added to the codes above

TH Ordinal number, (e.g. DDTH for 4th)

SP Spelled out number, (eg DDSP for FOUR)

SPTH to THSP Spelled out ordinal number, (e.g. DDSPTH for FOURTH)

Capitalisation in a spelled out word follows capitalisation in the corresponding format

element.

e.g. DAY produces output, such: MONDAY, Day produces Monday, day produces monday etc.

5.3.2 Times of Day

Oracle Dates also include the time of day. In order to display the time, merely include it in the

format model

e.g. COLUMN HIRE_DATE FORMAT A30;

SELECT ENAME,

TO_CHAR(HIREDATE,MONTH DD,YYYY HH:MIPM) HIRE_DATE

FROM EMP

WHERE DEPTNO = 20;

Try it and see! Note that if in a date value, no time is specified then the default value given is

12:00 AM.

5.3.3 Date Arithmetic

The arithmetic operations allowed on date fields are:

date+number adds a number of days to a date, producing a date

date-number subtracts a number of days from a fate, producing a date

date-date subtracts one date from another, giving a number of days

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e.g. SELECT ENAME, HIREDATE, HIREDATE+365 REVIEWDATE

FROM EMP

WHERE DEPTNO = 20;

Displays the Reviewdate which is defined as 365 days after the Hiredate

5.3.4 SYSDATE

There is a special column called SYSDATE, which returns the value of the current date and

time. It is NOT an actual column in a Table and is thus a pseudo-column.

e.g. SELECT ENAME, SYSDATE TODAYFROM EMP;

Displays the current date for each employee.

5.3.5 Date Functions

There are a number of built-in functions involving Dates. Some of them are:


ADD_MONTHS ADD_MONTHS(d,n) date d plus n months

GREATEST GREATEST (D1,D2) later of D1 and D2

LEAST LEAST (D1, D2) earlier of D1 and D2

LAST-DAY LAST_DAY(HIREDATE) last day of month containing

HIREDATE

MONTHS_BETWEEN MONTHS_BETWEEN(SYSDATE,HIREDATE)

months between HIREDATE and

today

NEXT_DAY NEXT_DAY(HIREDATE,FRIDAY)

date of first Friday after HIREDATE

ROUND ROUND(HIREDATE) rounds HIREDATE to the nearest

whole day

TO_CHAR TO_CHAR(HIREDATE,MM/DD/YY)

converts a date value to a char

value. The format of the char

value is determined by the

specified format

model. Default format used if 2nd

argument absent

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TO_DATE TO_DATE(CHARDATE,MM/DD/YY)

converts a char value containing

a date to a date value. The char

value is interpreted according

to the specified format.

Some Examples of Using Dates

1) Find the review dates of employees hired in the last year for Dept 20, assuming that the

reviewdate is a year after the hiredate.

e.g. COLUMN HIREDATE A9

COLUMN TODAY A9

COLUMN REVIEWDATE A10

SELECT ENAME, HIREDATE, SYSDATE TODAY, HIREDATE+365,

REVIEWDATE

FROM EMP

WHERE HIREDATE + 365 > SYSDATE

AND DEPTNO = 20;

This gives:

ENAME HIREDATE TODAY REVIEWDATE

SCOTT 15-MAY-85 10-DEC-85 15-MAY-86ADAMS 18-JUN-85 10-DEC-85 18-JUN-86

Assume that today is 10th Dec 1985.

2) Calculate the number of days until the review

e.g. COLUMN DAYS_TO_REVIEW A14

SELECT ENAME, HIREDATE, SYSDATE TODAY,

HIREDATE+365 - SYSDATE DAYS_TO_REVIEW,

HIREDATE+365 REVIEWDATE

FROM EMP

WHERE HIREDATE+365 > SYSDATE

AND DEPTNO=20;

This gives:

ENAME HIREDATE TODAY DAYS_TO_REVIEW REVIEWDATE

SCOTT 15-MAY-85 10-DEC-85 155.985995370370 15-MAY-86

3703703703703703

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ADAMS 18-JUN-85 10-DEC-85 189.986030092592 16-JUN-86

9259259259259259

Note that the examples work if there are 365 days in a year. The decimal fraction forDAYS_TO_REVIEW is unreadable. These points can be corrected by:

e.g. SELECT ENAME, HIREDATE, SYSDATE TODAY,

ROUND(ADD_MONTHS(HIREDATE,12)-SYSDATE) DAYS_TO_REVIEW

ADD_MONTHS(HIREDATE,12) REVIEWDATE

FROM EMP

WHERE ADD_MONTHS (HIREDATE,12)> SYSDATE

AND DEPTNO=20;

3) Suppose reviews are not exactly one year after the hiredate. Suppose that reviews are onthe first Friday after the employee has been working for a year and that rises are given on the

last day of the month of the review. NEXT_DAY and LAST_DAY can be used to calculate both

of these dates.

e.g. COLUMN RAISEDATE FORMAT A9;

SELECT ENAME, HIREDATE,

NEXT_DAY(ADD_MONTHS(HIREDATE,12),FRIDAY) REVIEWDATE,

LAST_DAY(NEXT_DAY(ADD_MONTHS(HIREDATE,12),FRIDAY) )

RAISEDATEFROM EMP

WHERE ADD_MONTHS (HIREDATE,12)>SYSDATE

AND DEPTNO = 20;

This gives:

ENAME HIREDATE REVIEWDATE RAISEDATE

SCOTT 15-MAY-85 16-MAY-86 31-MAY-86

ADAMS 18-JUN-85 20-JUN-86 30-JUN-86

Using dates in SQL commands

As well as in the SELECT clause you may use dates in other parts of SQL statements. in fact,

you can use a date value anywhere that you use a number or a char value, i.e. in WHERE,

ORDER BY and GROUP BY clauses. This is demonstrated through the following examples.

1) SELECT ENAME, HIREDATE

FROM EMP

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WHERE HIREDATE BETWEEN 4-JAN-84 AND 15-APR-84

ORDER BY HIREDATE;

2) SELECT TO_CHAR (HIREDATE,Q-Q YYYY) HIRE_DATE, COUNT(*)

FROM EMP

GROUP BY TO_CHAR (HIREDATE,YYYY Q-Q);

Note that this example counts the employees hired in each quarter of each year.

5.4 Handling Null Values

A Null value is different from zero or blank. It is used to illustrate that a particular data field

has not got a value in it yet, or that a value in that field would be inappropriate. e.g., in the

EMP table, only Salesmen have values in the Commission field as only salesmen getcommission. The empty commission field entries have Null values in them.

Null Conditions

Comparisons can be made with Null fields by using IS NULL, IS NOT NULL

e.g. Find the names of employees who are NOT entitled to commission.SELECT ENAME

FROM EMPWHERE COMM IS NULL;

e.g. Find the names of employees who are entitled to commission.SELECT ENAME

FROM EMP

WHERE COMM IS NOT NULL;

ORDER BY with NULL values

If the column involved in the ORDER BY has Null values then the tuples with the Null values

will appear first, whether the order is to be Ascending or Descending

Null values in Expressions and Functions

If a function or expression involves a column that contains a Null value, then the result is also

Null.

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e.g. If we wanted to form a column SAL+COMM then those tuples with Null values for COMM

will cause a value of Null for SAL+COMM

e.g. If we applied COUNT(COMM) then the COUNT function would return the number of non

Null values.

The Null Value function NVL

The form of the NVL function is

NVL(EXPRESSION, NON-NULL VALUE)

e.g. NVL(COMM,0)

would replace each null value of COMM with the value 0

e.g. NVL(HIREDATE,31-DEC-86)

would replace each null value of HIREDATE with the value 31-DEC-86

This is a useful feature, enabling us to include null-valued entries in our queries.

e.g. SELECT AVG(COMM), AVG(SAL+NVL(COMM,0))

FROM EMP

WHERE DEPTNO = 30;

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6. SUBQUERIES

A subquery is a query contained in a WHERE clause. It provides you with results that are

needed to complete the main query. Subqueries are useful when you want to select rows from

a table with a condition that depends upon data in the table itself.

e.g. SELECT ENAME, JOB

FROM EMP

WHERE JOB=

(SELECT JOB

FROM EMP

WHERE ENAME=JONES);

The subquery is contained in brackets. This subquery returns a single value, in this case

MANAGER.

The main query now becomes:


FROM EMP

WHERE JOB=MANAGER;

If the subquery had returned no values or more than one value, then an error message would

have been displayed.

Using ANY and ALL

Sometimes we want to use subqueries which return more than one value. In this situation we

use the ANY or ALL options.

e.g. SELECT DISTINCT SAL, JOB, ENAME, DEPTNO

FROM EMP

WHERE SAL > ANY

(SELECT SAL

FROM EMP

WHERE DEPTNO = 30);

Again, the subquery is contained in brackets. This query returns a set of all SAL values foremployees in Dept 30.

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The main query is now about looking at the EMP table for rows where the SAL value is greater

than ANY of the subquery set. That is any row where the SAL value is greater than the

smallest value of the subquery set.

The DISTINCT clause is necessary in order to avoid rows being chosen many times. e.g., the

PRESIDENT KING has a salary of $5000. Without the DISTINCT clause, the PRESIDENT row

would be returned every time that it was compared with the subquery set, since the

Presidents Sal is greater than ALL the subquery SAL values.

e.g. SELECT SAL, JOB, ENAME, DEPTNO

FROM EMP

WHERE SAL> ALL

(SELECT SAL

FROM EMP

WHERE DEPTNO=30);

The subquery is as before and returns the same set of SAL values. This time, however, the

main query returns those rows with SAL value greater than ALL the subquery set. Note that

there is no need for the DISTINCT clause this time.

ANY and ALL can be used with the operators ( =, , >, >=,


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(SELECT JOB

FROM EMP

WHERE DEPTNO = 30);

This lists the name and job of anybody in DEPT 10 with a job not done by anybody in DEPT 30.

Subqueries that return more than one column

So far, subqueries have returned a set of values based on one column only. However,

sometimes it would be useful to return groups of values, i.e. values for more than one column.

e.g. List employees with same job and salary as FORD.

e.g. SELECT ENAME, JOB, SALFROM EMP

WHERE (JOB,SAL)=

(SELECT JOB, SAL

FROM EMP

WHERE ENAME = FORD);

Multiple Subqueries

It is possible to have combinations of subqueries separated by AND or OR.

e.g. SELECT ENAME, JOB, DEPTNO, SAL

FROM EMP

WHERE JOB IN

(SELECT JOB

FROM EMP

WHERE ENAME = JONES)

OR SAL >=

(SELECT SAL

FROM EMPWHERE ENAME = FORD)

ORDER BY JOB, SAL;

This lists employees with either the same job as Jones or a salary greater than or equal to Fords

salary, in order of job and salary.

You can also put subqueries within subqueries with up to 16 levels.

e.g.SELECT ENAME, JOB

FROM EMP

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WHERE DEPTNO = 10

AND JOB IN

(SELECT JOB

FROM EMP

WHERE DEPTNO IN

(SELECT DEPTNO

FROM DEPT

WHERE DNAME = SALES));

This lists employees in Dept 10 with the same job as anyone in the Sales dept.

Note

A query or subquery may be composed of two or more queries with the operators UNION,

INTERSECT and MINUS.

UNION -- returns all distinct rows returned by EITHER of the queries it applies to.

INTERSECT -- returns all rows returned by BOTH of the queries it applies to.

MINUS -- returns all rows returned by the PRECEDING query but NOT by the FOLLOWING

query.

e.g. SELECT ENAME, JOB, SALFROM EMP

WHERE SAL IN

(SELECT SAL

FROM EMP

WHERE ENAME = SCOTT

UNION

SELECT SAL

FROM EMP

WHERE ENAME = WARD);

This lists employees whose salary is equal to that of Scott or Ward.

When applying the operators UNION, INTERSECT and MINUS for queries on different tables,

the results of these queries must be union-compatible. In the context of SQL, this means that

corresponding columns from the different results must match in both number of columns and

type of column. Type does not imply that they must be of the same length, and you cannot use

columns of type LONG.

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You can also use ORDER BY in the overall query. The ORDER BY must occur once only at the

end. Since corresponding columns in different tables might have different names, the ORDER

BY refers to the appropriate column by its order in the column list.

e.g. Consider two similar tables, PROJ_A, PROJ_B with appropriate columns.

e.g. SELECT ENAME, EMPNO, DEPT

FROM PROJ_A

UNION

SELECT EMPNAME, EMPNUM, DEPT

FROM PROJ_B

ORDER BY 2;

This lists employee details of employees who are in PROJ_A or PROJ_B, or both. The list isordered by column 2 (i.e. the employee number column).

Subqueries can refer to more than one table.

e.g. SELECT ENAME, LOC, JOB

FROM EMP, DEPT

WHERE LOC = CHICAGO

AND EMP.DEPTNO = DEPT.DEPTNO

AND JOB IN

(SELECT JOB

FROM EMP

WHERE ENAME = ALLEN)

ORDER BY ENAME;

This lists the employees located in Chicago with the same job as ALLEN, in ENAME order.

Correlated Subqueries

In previous examples each subquery was carried out once for the whole query. However, it ispossible to construct a query where the subquery is carried out once for each row of the main

query.e.g. SELECT DEPTNO, ENAME, SAL

FROM EMP X

WHERE SAL >

(SELECT AVG(SAL)

FROM EMP

WHERE X.DEPTNO = DEPTNO)

ORDER BY DEPTNO;

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This lists all employees who earn more than the average salary of employees in their own

departments (in dept order).

Note the ALIAS table name X for EMP. This means that X is a copy of the table EMP for use in

the main query. There is another table EMP for the subquery. What happens here is that table

X is scanned. The condition applied to each tuple of X is to check the SAL to see if it is greater

than the average SAL calculated on the EMP table of the subquery. The average is taken for

those rows where the DEPTNO is equal to current the DEPTNO value of the main query. This

means that the subquery is carried out once for each row of the X table.

EXISTS

A conditional expression EXISTS (subquery) can be written which returns 'true' if the

subquery returns at least one row and 'false' if there are no rows returned.

e.g. SELECT JOB, ENAME, DEPTNO

FROM EMP X

WHERE EXISTS

(SELECT *

FROM EMP

WHERE X.EMPNO = MGR);

This lists information about employees who have at least one other employee reporting to

them.

NOT EXISTS

A conditional expression NOT EXISTS (subquery) can be written which returns 'false' if the

subquery returns at least one row and 'true' if there are no rows returned.

e.g. SELECT JOB, ENAME, DEPTNO

FROM EMP X

WHERE NOT EXISTS

(SELECT *

FROM EMP

WHERE X.EMPNO = MGR);

This lists information about employees who do not have any employees reporting to them.

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7. CREATING, DROPPING and RENAMING TABLES

Previous chapters have dealt with Data Manipulation in the form of retrieval operations. This

chapter considers Data Definition. Since the only data structure is the table, data definition

involves the definition of tables.

The SQL statement which does this is the CREATE TABLE statement. The format of the

CREATE TABLE statement is

CREATE TABLE table-name

(column-definition, column-definition, ...... column-definition);

where column-definition = column-name column-format [NOT NULL].

e.g. CREATE TABLE DOCTOR

(DOCTOR_NO CHAR(4) NOT NULL,

DOCTOR_NAME CHAR(20),

DATE_OF_BIRTH DATE,

FEE_RATE NUMBER(6,2));

This creates a table with 4 columns. The DOCTOR_NO column is made up of at most 4

characters and NULL values are not allowed in this column. The column for DOCTOR_NAME

is up to 20 characters. The DATE_OF_BIRTH is of data type Date and the FEE_RATE column

has at most 6 numeric digits of which 2 are after a decimal point.

Specifying primary and foreign keys

At the time a table is created it is possible to define both primary and foreign keys. Let us

assume that two tables are to be created (TEMP1 and TEMP2) which participate in a foreign

key relationship. The CREATE TABLE command could be used in the following way:

CREATE TABLE TEMP1

(COL1 CHAR(5),

COL2 NUMBER(4),

COL3 CHAR(10),

CONSTRAINT PK_FIRSTCOL PRIMARY KEY (COL1),

CONSTRAINT FK_COL FOREIGN KEY (COL3) REFERENCES TEMP2(COL1));

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CREATE TABLE TEMP2

(COL1 CHAR(10),

COL2 DATE,

CONSTRAINT PK_TEMP2 PRIMARY KEY (COL1));

It is also possible to set up both priamry and foriegn keys that are made up of more than just

one column.

7.1 Data types

The data types supported for columns are:-Data Type May contain

CHAR(w) This is a fixed length data type where char values consisting

of upper and lower case letters numbers and special characters

(+, -, %, $, &, etc.). w is the width which is the maximum length

in characters. w must not exceed 240.

VARCHAR2(w) This is a variable length data type where char values consisting

of upper and lower case letters numbers and special characters

(+, -, %, $, &, etc.). w is the width which is the maximum length

in characters. w must not exceed 480. Here varying sizes of data

can be stored and only the necessary amount of storage is allocated.

NUMBER number values consisting of the digits 0-9 with an optional sign

(+ or -) and a decimal point. Values may be 40 digits wide.

NUMBER(w) numbers up to w digits wide. w may not exceed 105. Thenumber of significant digits may not exceed 40

even if w is greater than 40.

NUMBER(w,d) d of the digits are to the right of the decimal point.

DATE date values from Jan 1, 4712 BC to Dec 31, 4712 AD.

LONG similar to CHAR but values may be up to 65,535 characters

long. No more than one LONG column can be defined fora table.

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VALUES (list of data values)

e.g. INSERT INTO EMP

VALUES (7954, 'CARTER', 'CLERK', 7698, '7-APR-93', 1000, NULL, 30);

...... adds a new row into EMP.

e.g. INSERT INTO EMP (EMPNO, ENAME, HIREDATE, DEPTNO, SAL)

VALUES (7655, 'WILSON', '22-APR-93', 30, 1500);

...... adds values into the chosen columns only. Any columns not listed will have NULL values

added. An attempt to put NULL into a NOT NULL field will cause an error.

8.1.1 Inserting Date Values

Date formats

When a value is added into a date column it must be in standard date format, i.e. DD-MON-YY

(01-JAN-93). A function (TO_DATE) is available to convert any date in another format to

standard format. TO_DATE has two arguments: the first is the date value that you wish to add

and the second is the format of that date value.


VALUES (7657, 'MASON', 'ANALYST', 7566,

TO_DATE('4/24/93', 'MM/DD/YY), 3400, NULL, 20);

....... takes a date in the form 4/24/93 and converts it to the standard form before insertion.

Time of Day

If you want to put in a time of day as well as a date then use:-


VALUES (7658, 'CHAN', 'ANALYST', 7566,

TO_DATE('3-MAY-93 9:30', 'DD-MON-YY HH:MI'), 3000, NULL, 20);

8.1.2 Copying rows between tables.

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It is possible to copy rows between tables (i.e. from one table to another) by using a subquery

in the INSERT statement.

e.g. INSERT INTO BONUS (ENAME, JOB, SAL, COMM)SELECT ENAME, JOB, SAL, COMM

FROM EMP

WHERE JOB = 'MANAGER'

OR COMM > 0.25 * SAL;

...... copies rows into the BONUS table where the employee is a Manager or the commission is

more than a quarter of the salary.

You can create and insert at the same time by using:-

e.g. CREATE TABLE BONUS (ENAME, JOB, SAL, COMM)

AS (SELECT ENAME, JOB, SAL, COMM

FROM EMP

WHERE JOB = 'MANAGER'

OR COMM > 0.25 * SAL);

Note that BONUS must not already exist as either a table or a synonym.

8.1.3 Multiple Insertion

When more than one row is to be inserted, the symbol & may be used before each attribute in

the VALUES clause to obviate repeating the INSERT

e.g. INSERT INTO EMP VALUES (&EMPNO, '&ENAME', '&HIREDATE',

&DEPTNO, &SAL);

When the INSERT is run, enter the data for the first row at the prompt. Then use the run

symbol '/' to repeat the process for each successive row.

8.2 UPDATE

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Updating values in a table is achieved using the UPDATE statement. The format of the

UPDATE command is:-

UPDATE table-name

SET field = value, field = value, ......WHERE condition;

e.g. UPDATE EMP

SET JOB = 'SALESMAN', HIREDATE = SYSDATE, SAL = 1.1 * SAL

WHERE ENAME = WILSON;

....... assigns Wilson to the sales staff and gives him/her a 10% rise in salary.

Updating can be carried on several rows at a time:-

e.g. UPDATE EMP

SET SAL = SAL * 1.15

WHERE (JOB = 'ANALYST' OR JOB = 'CLERK')

AND DEPTNO = 20;

....... gives a 15% rise to all Analysts and Clerks in department 20.

UPDATE statements can also include subqueries:-

e.g. UPDATE EMP

SET SAL = SAL * 1.05

WHERE ENAME IN

(SELECT ENAME

FROM BONUS);

....... gives a 5% rise to anybody entitled to a bonus.

e.g. UPDATE EMPSET SAL =

(SELECT 1.1 * AVG(SAL)

FROM EMP

WHERE JOB = 'SALESMAN')

WHERE JOB = 'SALESMAN';

....... sets all salesmen's salaries to 110% of the average salesman salary.

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8.3 DELETE

Deleting information from tables is achieved using the DELETE statement. The format of the

DELETE statement is:-

DELETE FROM table-name

WHERE condition;

e.g. DELETE FROM BONUS

WHERE ENAME = 'WARD';

....... deletes Ward from the bonus table.

Several rows may be deleted at once by a suitable WHERE clause which may include a

subquery if necessary.

e.g. DELETE FROM BONUS

WHERE JOB IN

(SELECT JOB

FROM EMP

WHERE ENAME = 'JONES');

....... deletes all employees from the BONUS table with the name job as Jones.

8.4 Committing database changes

When changes are made to the database tables they may or may not be made permanent. The

action of making changes permanent is known as COMMITTING. The default upon entering

SQLPLUS is that changes will not normally be made permanent until you exit from SQLPLUS

or you issue certain statements. (i.e. ALTER, AUDIT, CREATE, DISCONNECT, DROP, EXIT,

GRANT, NOAUDIT, QUIT, or REVOKE)

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Thus in a normal situation when updates are deletes or inserts are made they will be visible if

you inspect the tables but can be 'undone' by the issue of a ROLLBACK statement. If you wish

to make changes permanent enter COMMIT.

It is possible to arrange things such that changes are committed as soon as they are carried out.This can be achieved using the AUTOCOMMIT facility. The options are:-

SQL> SET AUTOCOMMIT IMMEDIATE - turns the autocommit on

SQL >SET AUTOCOMMIT ON - turns the autocommit on

SQL> SET AUTOCOMMIT OFF - turns autocommit off (default)

Note that after insertion of values into a table, the new records are not always committed. Be

safe by issuing a commit at the prompt.

9. MODIFYING A TABLE

Sometimes the definition of a table might become inappropriate. We look here at the way we

can make two changes to a table: enlarge a column, and add a column.

Enlarging a column

The format is

ALTER TABLE table-name

MODIFY (new column-definition);

e.g. ALTER TABLE PROJ

MODIFY (BUDGET NUMBER(9,2));

...... changes the budget column to 9 digits with 2 decimal places.

You can change a format from NOT NULL to NULL but you can only change a column format

from NULL to NOT NULL if there are no null values in the appropriate column.

Adding a column

The format is

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ALTER TABLE table-name

ADD (column-definition);

e.g. ALTER TABLE EMP

ADD (PROJNO NUMBER);

The new column will appear to the right of existing columns and will initially have all of it's

values as NULL.

10. VIEWS

One of the most important facilities of a DBMS is the provision of user views. That is, the

provision of mechanisms that allow the 'subsetting' of the centralised data resource in order to

reflect individual perceptions of users.

The view facility provides a level of security against inadvertent or deliberate inspection of

sensitive data. Views can also help with complex query processing in that SQL statements canbe directed against views as opposed to the original tables.

10.1 Creating a view

The format for the view statement is:-

CREATE VIEW view-name

AS query;

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e.g. CREATE VIEW EMP10

AS SELECT EMPNO, ENAME, JOB

FROM EMP

WHERE DEPTNO = 10;

This defines a view of department 10 of the EMP table.

Note that. the query in the CREATE VIEW may be any valid query but MUST NOT contain an

ORDER BY clause. Any ordering must be carried out when the view is queried.

You may create views from already defined views.

View tables do not actually exist in the database. They are 'virtual tables'.

10.2 Querying a view

e.g. SELECT *

FROM EMP10;

........ displays the contents of the view EMP10.


FROM EMP10WHERE EMPNO > 7800;

....... picks rows from the view.

When you change data in a base table the views which involve the updated rows/columns

reflect the changes made.

e.g. UPDATE EMP

SET JOB = 'ANALYST'WHERE ENAME = 'MILLER';

....... changes Miller's job to analyst. If we now look at the view EMP10 we would see the

change of Miller's job to analyst.

10.3 Updating a view

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It may or may not be possible to carry out update operations directly on a view. For a view to

be updatable the query in the CREATE VIEW statement must obey the following rules:-

a) It must refer to only one table.

b) It does not contain a GROUP BY clause, a DISTINCT clause, a group function, or a reference

to the pseudo column ROWNUM.

You may delete rows from a view if a) and b) occur. You may insert (add) rows into a view if a)

and b) are satisfied and:-

c) It contains no columns defined by expressions.

Thus in order to change Miller's job to clerk, we can use:-

e.g. UPDATE EMP10

SET JOB = 'CLERK'

WHERE ENAME = 'MILLER';

10.4 Views of more than one table

A view which contains data from more than table can be created by using joins to connect the

tables,e.g. CREATE VIEW PROJSTAFF (EMPLOYEE, PROJECT, PROJECT_NUMBER)

AS SELECT ENAME, PNAME, EMP.PROJNO

FROM EMP, PROJ

WHERE EMP.PROJNO = PROJ.PROJNO;

This creates a view called PROJSTAFF with the columns renamed as EMPLOYEE(was

ENAME), PROJECT(was PNAME) and PROJECT_NUMBER(was EMP.PROJNO).

e.g. SELECT EMPLOYEE, PROJECT

FROM PROJSTAFF

WHERE PROJECT_NUMBER = 101;

10.5 Using expressions and functions in views

In the creation of a view the query that defines it may contain derived columns obtained from

expressions on columns in the underlying tables.

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11. REPORTING COMMANDS

ORACLE provides facilities to improve the appearance of information displayed by a query.

11.1 Page formatting

The word page refers to a screenful of information on your display, or a page of a spooled

report.

The following commands can be issued at the SQL prompt to reformat the page:

SET LINESIZE nn defines width of page (default is 80, maximum is 132).

SET PAGESIZE nn defines length of page (default is 19).

SET SPACE nn defines number of horizontal spaces between columns.

SET NEWPAGE nn defines number of blank lines at end of page.

SET PAUSE stops screen from scrolling.

11.2 Report titles

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It is possible to define titles which can appear at the top or the bottom of each page of a report.

TTITLE defines a title that appears at the top of each page.

BTITLE defines a title that appears at the bottom of each page.

Both these title commands can take various clauses:

LEFT places the values at the beginning of the line.

RIGHT places the values at the end of the line.

CENTER places the values at the center of the line (based on LINESIZE).

SKIP n begin a new line or begin n new lines.

| stack the title.

- continuation character.

Example:

TTITLE CENTER Company Confidential Report SKIP 1

LEFT Sales for first Quarter RIGHT Computing Department SKIP 2;

Would display the following heading at the top of every page of output:

Company Confidential Report

Sales for first Quarter Computing Department

Example:

BTITLE CENTER Draft submission

Would display the following at the bottom of each page of output:

Draft submission

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11.3 Formatting columns

Columns of a table can be given new headings and new formats for the duration of the query.

A more meaningful column heading can be displayed with the use of the COLUMN command:

COLUMN HEADING

Note that '|' can be used in to stack the heading.

Example:

COLUMN ENAME HEADING Employee| Name;

You can change the displayed width of a column by:

COLUMN FORMAT

The is defined so that 'A' is used for character columns and '9' is used for numericcolumns.

Example:

COLUMN SAL HEADING Salary FORMAT 99,999;

Or

COLUMN ENAME FORMAT A10;

The COLUMN command can also be used to suppress the display of a named column:

COLUMN NOPRINT

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11.4 Structuring a report

Control breaks can be used to structure a report into groups by the value of a column. All rows

with the same value in that column are organised into a group.

The BREAK command is used to organise the rows into groups.

BREAK ON *must also use the SELECT's ORDER BY clause.

Other breaks:

BREAK ON ROW whenever a row is retrieved.

BREAK ON PAGE at the end of a page.

BREAK ON REPORT at the end of a report.

Various types of action can be taken at breaks, e.g. an empty line can be displayed (SKIP) or a

new page can be started (PAGE).

After organising rows into groups with the BREAK, you can make the query perform

computations on rows in the group. For example you can make a query compute subtotals on a

specified column for the rows in each group as follows:

COMPUTE SUM OF ON

Any GROUP BY function can be used with COMPUTE, for example MAX, AVG and COUNT.

Example:

BREAK ON DEPTNO;

COMPUTE SUM OF SAL ON DEPTNO;

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11.5 Displaying variable information in titles

To display the page number in the title:

TTITLE RIGHT 'Page' SQL.PNO;

To display column values and special values such as SYSDATE in the title, use has to be made

of a variable which can then be referenced by the TTITLE (or BTITLE) command.

The sequence of commands is:

COLUMN TODAY NEW_VALUE DATEVAR;

This creates a variable DATEVAR to hold the value of the current date.

TTITLE LEFT DATEVAR;

Now that variable can be referenced in the TTITLE command.

COLUMN TODAY NOPRINT;

Usually if you print the value of a variable in the title, you do not want it to appear again in the

body of the report.

Now add SYSDATE to the SELECT command:

SELECT TO_CHAR(SYSDATE, 'DD/MM/YY') TODAY .......;

The same sequence can be followed for any column in a table.

11.6 Saving reporting commands

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Normally, when SQLPLUS is entered, the input from the keyboard is taken into the default

SQL buffer. However, when we enter formatting statements, for example, which change the

current definitions of Column Formats, these are not taken into this normal buffer.

Any attempt to SAVE the current work as afiedt.buf, for instance, will cause only the SQLstatement to be saved in the file. The formatting statements will not be saved. In order to

SAVE the formatting statements as well, we must use the save as option to create a new file.

Remember to give this file a new name with the usual .sql extension.

When you are ready to run the file with the formatting commands in it simply use the

following:

@filename.sql

Note that the @ symbol means run the contents of the file.

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APPENDIX 1 The Sample Tables

Note: These are the sample tables which ORACLE comes with - there may be differences in

the some of the data values.

EMP

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTN

7369

7499

7521

7566

76547698

7782

7788

7839

7844

7876

7900

7902

7934

SMITH

ALLEN

WARD

JONES

MARTINBLAKE

CLARK

SCOTT

KING

TURNER

ADAMS

JAMES

FORD

MILLER

CLERK

SALESMAN

SALESMAN

MANAGER

SALESMAN

MANAGER

MANAGER

ANALYST

PRESIDENT

SALESMAN

CLERK

CLERK

ANALYST

CLERK

7902

7698

7698

7839

7698

7839

7839

7566

7698

7788

7698

7566

7782

17-DEC-80

20-FEB-81

22-FEB-81

02-APR-81

28-SEP-81

01-MAY-81

09-JUN-81

09-DEC-82

17-NOV-81

08-SEP-81

12-JAN-83

03-DEC-81

03-DEC-81

23-JAN-82

800.00

1,600.00

1,250.00

2,975.00

1,250.00

2,850.00

2,450.00

3,000.00

5,000.00

1,500.00

1,100.00

950.00

3,000.00

1,300.00

300.00

500.00

1,400.00

0.00

20

30

30

20

30

30

10

20

10

30

20

30

20

10

DEPT

DEPTNO DNAME LOC

10

20

30

40

ACCOUNTING

RESEARCH

SALES

OPERATIONS

NEW YORK

DALLAS

CHICAGO

BOSTON

SALGRADE

GRADE LOSAL HISAL

1

2

3

4

5

70 0

1201

1401

2001

3001

1200

1400

2000

3000

9999

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