PL/SQLPL/SQL Oracle10g Developer: PL/SQL Programming Chapter 3 Handling Data in PL/SQL Blocks.
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Transcript of PL/SQLPL/SQL Oracle10g Developer: PL/SQL Programming Chapter 3 Handling Data in PL/SQL Blocks.
PL/SQL
Oracle10g Developer: PL/SQL Programming
Chapter 3
Handling Data inPL/SQL Blocks
PL/SQL
Oracle10g Developer: PL/SQL Programming 2
Chapter Objectives
• After completing this lesson, you should be able to understand:– SQL queries within PL/SQL
– Host or bind variables
– The %TYPE attribute
– Expanding block processing to include queries and control structures
PL/SQL
Chapter Objectives (continued)
• After completing this lesson, you should be able to understand (continued):– Embedding DML statements within PL/SQL
– Composite data types
– Creating collections
– Understanding the GOTO statement
Oracle10g Developer: PL/SQL Programming 3
PL/SQL
Oracle10g Developer: PL/SQL Programming 4
Brewbean’s Challenge
• Consider actions needed upon check out
PL/SQL
Oracle10g Developer: PL/SQL Programming 5
Include SQL within a Block
• Data query needs to identify if the customer has a saved basket
PL/SQL
Oracle10g Developer: PL/SQL Programming 6
Include SQL within a Block (continued)
• SQL statements can be embedded into the executable area of a PL/SQL block
• SELECT statements are embedded to query needed data
• An INTO clause is added to a SELECT statement to move data retrieved into variables
PL/SQL
Oracle10g Developer: PL/SQL Programming 7
Include SQL within a Block (continued)
SQL Query – add INTO clause
Assignment Statement
PL/SQL
Oracle10g Developer: PL/SQL Programming 8
Executing a Block with Errors
• Common Errors– Use = rather than :=
– Not declaring a variable
– Misspelling a variable name
– Not ending a statement with ;
– No data returned from a SELECT statement
PL/SQL
Oracle10g Developer: PL/SQL Programming 9
Executing a Block with Errors (continued)
• Not closing a statement with ;
PL/SQL
Oracle10g Developer: PL/SQL Programming 10
Host or Bind Variables
• Reference host variables with a preceding colon in PL/SQL
BEGIN
:g_shopper := 25;
END;
/
WHERE idShopper = :g_shopper
AND orderplaced = 0;
Create host variable
Reference host variable
PL/SQL
Oracle10g Developer: PL/SQL Programming 11
%TYPE Attribute
• Use in variable declaration to provide data type based on a table column
• Ideal for declaring variables that will hold data from the database
• Minimizes maintenance by avoiding program changes to reflect database column changes
• Called an anchored data type
lv_basket_num bb_basket.idBasket%TYPE;
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Oracle10g Developer: PL/SQL Programming 12
Data Retrieval with Decision Structures
PL/SQL
Oracle10g Developer: PL/SQL Programming 13
IF Statement Example
PL/SQL
Oracle10g Developer: PL/SQL Programming 14
Including DML
• DML statements can be embedded into PL/SQL blocks to accomplish data changes
• DML includes INSERT, UPDATE, and DELETE statements
PL/SQL
Oracle10g Developer: PL/SQL Programming 15
Including DML (continued)
• Add a new shopper - INSERT
PL/SQL
Oracle10g Developer: PL/SQL Programming 16
Composite Data Types
• Stores multiple values of different data types as one unit
• Record – can hold one row of data• Table of records – can hold multiple rows of
data
PL/SQL
Oracle10g Developer: PL/SQL Programming 17
Record Data Type
DECLARE TYPE type_basket IS RECORD ( basket bb_basket.idBasket%TYPE, created bb_basket.dtcreated%TYPE, qty bb_basket.quantity%TYPE, sub bb_basket.subtotal%TYPE); rec_basket type_basket; lv_days_num NUMBER(3); lv_shopper_num NUMBER(3) := 25;BEGIN SELECT idBasket, dtcreated, quantity, subtotal INTO rec_basket FROM bb_basket WHERE idShopper = lv_shopper_num AND orderplaced = 0; lv_days_num := SYSDATE - rec_basket.created;END;
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Oracle10g Developer: PL/SQL Programming 18
%ROWTYPE Attribute
• Create record structure based on table structure
DECLARE rec_shopper bb_shopper%ROWTYPE;BEGIN SELECT * INTO rec_shopper FROM bb_shopper WHERE idshopper = :g_shopper; DBMS_OUTPUT.PUT_LINE(rec_shopper.lastname); DBMS_OUTPUT.PUT_LINE(rec_shopper.address); DBMS_OUTPUT.PUT_LINE(rec_shopper.email);END;
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Oracle10g Developer: PL/SQL Programming 19
Table of Records
PL/SQL
Oracle10g Developer: PL/SQL Programming 20
Collections
• Store multiple values of the same data type• Similar to arrays in other languages• Index-by Tables – handle many rows of one
field
One-dimensional
Can only have one column
Unconstrained Rows added dynamically as needed
Sparse A row only exists when a value is assigned; rows do not have to be assigned sequentially
Homogeneous All elements have same data type
Indexed Integer index serves as primary key of the table
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Oracle10g Developer: PL/SQL Programming 21
Index-by Table Attributes
Attribute Name
Value Data type Description
COUNT NUMBER Number of rows in the table
DELETE None Removes a row from the table
EXISTS BOOLEAN TRUE if specified row does exist
FIRST BINARY_INTEGER Index for the first row in the table
LAST BINARY_INTEGER Index for the last row in the table
NEXT BINARY_INTEGER Index for the next row in the table after the row specified
PRIOR BINARY_INTEGER Index for the row in the table before the row specified
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Oracle10g Developer: PL/SQL Programming 22
Index-by Table Example
Host variables declaration and initialization
PL/SQL
Oracle10g Developer: PL/SQL Programming 23
Index-by Table Example
Put host variable values into the table variable
A FOR loop adds all the sample measurements that have been entered
into the table variable
lv_avg_num calculates the Average measurement
Index-by table data type declaration
Index-by table variable declaration
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Oracle10g Developer: PL/SQL Programming 24
GOTO Statement
• Jumping control that instructs the program to move to another area of code to continue processing
• Most developers discourage the use of GOTO as it complicates the flow of execution
PL/SQL
Oracle10g Developer: PL/SQL Programming 25
Summary
• SQL queries and DML statements can be embedded into a block
• An INTO clause must be added to a SELECT• The %TYPE attribute is used to use a column
data type• Composite data types can hold multiple values
in a single variable
PL/SQL
Oracle10g Developer: PL/SQL Programming 26
Summary (continued)
• A record can hold a row of data• A table of records can hold multiple rows of
data• The %ROWTYPE attribute can be used to
declare a data type based on a table’s structure
• An index-by table is a collection similar to arrays
• The GOTO statement enables execution to jump to specific portions of code