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IS 4420Database Fundamentals

Chapter 7:Introduction to SQL

Leon Chen



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Systems DevelopmentLife Cycle

Project Identificationand Selection

Project Initiation

and Planning Analysis

Physical Design

Implementation

Maintenance

Logical Design

Enterprise modeling

Conceptual data modeling

Logical database design

Physical database designand definition

Database implementation

Database maintenance

DatabaseDevelopment Process



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Part Four: Implementation

Chapter 7 – Introduction to SQLChapter 8 – Advanced SQLChapter 9 – Client/Server EnvironmentChapter 10 – Internet

Chapter 11 – Data Warehousing



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Overview

Define a database using SQL datadefinition languageWork with ViewsWrite single table queriesEstablish referential integrity



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SQL OverviewStructured Query LanguageThe standard for relational databasemanagement systems (RDBMS)SQL-92 and SQL-99 Standards – Purpose:

Specify syntax/semantics for data definition andmanipulationDefine data structuresEnable portabilitySpecify minimal (level 1) and complete (level 2)standards

Allow for later growth/enhancement to standard



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SQL EnvironmentCatalog

A set of schemas that constitute the description of adatabase

SchemaThe structure that contains descriptions of objectscreated by a user (base tables, views, constraints)

Data Definition Language (DDL)Commands that define a database, including creating,altering, and dropping tables and establishingconstraints

Data Manipulation Language (DML)Commands that maintain and query a database

Data Control Language (DCL)Commands that control a database, includingadministering privileges and committing data



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SQL Database DefinitionData Definition Language (DDL)Major CREATE statements:

CREATE SCHEMA – defines a portion of thedatabase owned by a particular userCREATE TABLE – defines a table and its columnsCREATE VIEW – defines a logical table from oneor more views

Other CREATE statements: CHARACTER SET,COLLATION, TRANSLATION, ASSERTION,DOMAIN



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The following slides create tables forthis enterprise data model



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Non-nullable specification

Identifying primary key

Primary keyscan never have

NULL values

Create PRODUCT table



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Non-nullable specifications

Primary key

Some primary keys are composite – composed of multiple attributes



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Default value

Domain constraint

Controlling the values in attributes



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Primary key of parent table

Identifying foreign keys and establishing relationships

Foreign key ofdependent table



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Data Integrity ControlsReferential integrity – constraint thatensures that foreign key values of atable must match primary key values of

a related table in 1:M relationshipsRestricting:Deletes of primary recordsUpdates of primary recordsInserts of dependent records



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Using and Defining Views Views provide users controlled access to tables

Base Table – table containing the raw dataDynamic View

A “virtual table” created dynamically upon request by a userNo data actually stored; instead data from base table madeavailable to userBased on SQL SELECT statement on base tables or otherviews

Materialized ViewCopy or replication of dataData actually storedMust be refreshed periodically to match the correspondingbase tables



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Advantages of ViewsSimplify query commands

Assist with data security (but don't rely on viewsfor security, there are more important securitymeasures)Enhance programming productivityContain most current base table dataUse little storage space

Provide customized view for userEstablish physical data independence



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Disadvantages of ViewsUse processing time each time view isreferencedMay or may not be directly updateable



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Create Four ViewsCREATE VIEW CUSTOMER_V AS SELECT * FROM CUSTOMER_T;

CREATE VIEW ORDER_V AS SELECT * FROM ORDER_T;

CREATE VIEW ORDER_LINE_V AS SELECT * FROM ORDER_LINE_T;

CREATE VIEW PRODUCT_V AS SELECT * FROM PRODUCT_T;

„* is the wildcard



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Schema DefinitionControl processing/storage efficiency:

Choice of indexesFile organizations for base tablesFile organizations for indexesData clustering

Statistics maintenanceCreating indexes

Speed up random/sequential access to base tabledata

ExampleCREATE INDEX NAME_IDX ONCUSTOMER_T(CUSTOMER_NAME)This makes an index for the CUSTOMER_NAME field ofthe CUSTOMER_T table



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Insert Statement

Adds data to a tableInserting a record with all fieldsINSERT INTO CUSTOMER_T VALUES (001, „ContemporaryCasuals , 1355 S. Himes Blvd. , „Gainesville , „FL , 32601);

Inserting a record with specified fieldsINSERT INTO PRODUCT_T (PRODUCT_ID, PRODUCT_DESCRIPTION,PRODUCT_FINISH, STANDARD_PRICE, PRODUCT_ON_HAND) VALUES(1, „End Table , „Cherry , 175, 8);

Inserting records from another tableINSERT INTO CA_CUSTOMER_T SELECT * FROM CUSTOMER_T WHERESTATE = „CA ;



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Delete Statement

Removes rows from a tableDelete certain rows

DELETE FROM CUSTOMER_T WHERE STATE= „HI ;

Delete all rowsDELETE FROM CUSTOMER_T;



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SELECT StatementUsed for queries on single or multiple tablesClauses of the SELECT statement:

SELECTList the columns (and expressions) that should be returned from the query

FROMIndicate the table (s) or view(s) from which data will be obtained

WHEREIndicate the conditions under which a row will be included in the result

GROUP BYIndicate columns to group the results

HAVINGIndicate the conditions under which a group will be included

ORDER BYSorts the result according to specified columns



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Figure 7-8: SQL statementprocessing order



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SELECT Example using Alias

Alias is an alternative column or table name

SELECTCUST.CUSTOMER ASNAME,CUST.CUSTOMER_ADDRESS

FROM CUSTOMER_VCUSTWHERE NAME = „Home Furnishings ;



SELECT E l



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SELECT Example – Sorting Results with the ORDER BY Clause

Sort the results first by STATE, and within astate by CUSTOMER_NAME

SELECT CUSTOMER_NAME, CITY, STATEFROM CUSTOMER_VWHERE STATE IN („FL , „TX , „CA , „HI ) ORDER BY STATE, CUSTOMER_NAME;

Note: the IN operator in this example allows you to include rows whoseSTATE value is either FL, TX, CA, or HI. It is more efficient than separateOR conditions

SELECT E l



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SELECT Example – Categorizing Results Using the GROUP BY Clause

SELECT STATE, COUNT(STATE)FROM CUSTOMER_VGROUP BY STATE;

Note: you can use single-value fields withaggregate functions if they are included in the

GROUP BY clause

Customer table

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SELECT Example – Qualifying Results by Categories

Using the HAVING Clause

For use with GROUP BY

SELECT STATE, COUNT(STATE)FROM CUSTOMER_VGROUP BY STATEHAVING COUNT(STATE) > 1;

Like a WHERE clause, but it operates on groups (categories),not on individual rows. Here, only those groups with totalnumbers greater than 1 will be included in final result

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