Oracle_PLSQL.ppt ..
- 2. PL/SQL PL/SQL Originally modeled after ADA Originally modeled after ADA • Created for Dept. of Defense Created for Dept. of Defense Allows expanded functionality of Allows expanded functionality of database applications database applications Continues to improve with each new Continues to improve with each new database release database release
- 3. PL/SQL PL/SQL Features Features • Tight integration with SQL Tight integration with SQL Supports data types, functions, pseudo-columns, etc. Supports data types, functions, pseudo-columns, etc. • Increased performance Increased performance A block of statements sent as a single statement A block of statements sent as a single statement • Increased productivity Increased productivity Same techniques can be used with most Oracle Same techniques can be used with most Oracle products products • Portability Portability Works on any Oracle platform Works on any Oracle platform • Tighter security Tighter security Users may access database objects without granted Users may access database objects without granted privileges privileges
- 4. PL/SQL Programs PL/SQL Programs Declaration section (optional) Declaration section (optional) • Any needed variables declared here Any needed variables declared here Executable or begin section Executable or begin section • Program code such as statements to Program code such as statements to retrieve or manipulate data in a table retrieve or manipulate data in a table Exception section (optional) Exception section (optional) • Error traps can catch situations which Error traps can catch situations which might ordinarily crash the program might ordinarily crash the program
- 5. PL/SQL Block Structure PL/SQL Block Structure
- 6. PL/SQL Variables PL/SQL Variables Variables are local to the code block Variables are local to the code block Names can be up to 30 characters long and Names can be up to 30 characters long and must begin with a character must begin with a character Declaration is like that in a table Declaration is like that in a table • Name then data type the semi-colon Name then data type the semi-colon • Can be initialized using := operator in the Can be initialized using := operator in the declaration declaration • Can be changed with := in the begin section Can be changed with := in the begin section • Can use constraints Can use constraints Variables can be composite or collection Variables can be composite or collection types types • Multiple values of different or same type Multiple values of different or same type
- 7. Common PL/SQL Data Types Common PL/SQL Data Types • CHAR ( max_length ) CHAR ( max_length ) • VARCHAR2 ( max_length ) VARCHAR2 ( max_length ) • NUMBER ( precision, scale ) NUMBER ( precision, scale ) • BINARY_INTEGER – more efficient than BINARY_INTEGER – more efficient than number number • RAW ( max_length ) RAW ( max_length ) • DATE DATE • BOOLEAN (true, false, null) BOOLEAN (true, false, null) • Also LONG, LONG RAW and LOB types but the Also LONG, LONG RAW and LOB types but the capacity is usually less in PL/SQL than SQL capacity is usually less in PL/SQL than SQL
- 8. PL/SQL Variable Constraints PL/SQL Variable Constraints NOT NULL NOT NULL • Can not be empty Can not be empty CONSTANT CONSTANT • Can not be changed Can not be changed
- 9. PL/SQL Variables Examples PL/SQL Variables Examples Age number; Age number; Last char ( 10 ); Last char ( 10 ); DVal Date := Sysdate; DVal Date := Sysdate; SID number not null; SID number not null; Adjust constant number := 1; Adjust constant number := 1; CanLoop boolean := true CanLoop boolean := true
- 10. Predefined Exceptions Predefined Exceptions INVALID_NUMBER (ORA-01722) INVALID_NUMBER (ORA-01722) • Attempted to store non-numeric data in a Attempted to store non-numeric data in a variable with a numeric data type variable with a numeric data type NO_DATA_FOUND (ORA-01403) NO_DATA_FOUND (ORA-01403) • Query resulted in no rows being found Query resulted in no rows being found NOT_LOGGED_ON (ORA-01012) NOT_LOGGED_ON (ORA-01012) • Not currently connected to an Oracle Not currently connected to an Oracle database database TOO_MANY_ROWS (ORA-01422) TOO_MANY_ROWS (ORA-01422) • A SELECT INTO statement returned more A SELECT INTO statement returned more than one row than one row
- 11. Predefined Exceptions (cont.) Predefined Exceptions (cont.) DUP_VALUE_ON_INDEX (ORA-00001 DUP_VALUE_ON_INDEX (ORA-00001) ) • Value inserted for a primary key is not Value inserted for a primary key is not unique unique VALUE_ERROR VALUE_ERROR ( (ORA-06502 ORA-06502) ) • The value being placed in a variable is the The value being placed in a variable is the wrong length or data type wrong length or data type ZERO_DIVIDE (ORA-01476) ZERO_DIVIDE (ORA-01476) • An attempt was made to divide a number An attempt was made to divide a number by zero by zero
- 12. Structure of Exception Section Structure of Exception Section
- 13. Conditional Structures Conditional Structures IF-THEN IF-THEN IF-THEN-ELSE IF-THEN-ELSE IF-THEN-ELSIF IF-THEN-ELSIF • An alternative to nested IF-THEN_ELSE An alternative to nested IF-THEN_ELSE
- 18. Stored Procedures Stored Procedures The first line is called the The first line is called the Procedure Procedure Specification Specification The remainder is the The remainder is the Procedure Body Procedure Body A procedure is compiled and loaded A procedure is compiled and loaded in the database as an object in the database as an object Procedures can have parameters Procedures can have parameters passed to them passed to them
- 19. Stored Procedures Stored Procedures Run a procedure with the PL/SQL Run a procedure with the PL/SQL EXECUTE command EXECUTE command Parameters are enclosed in Parameters are enclosed in parentheses parentheses
- 20. Stored Functions Stored Functions Like a procedure except they return Like a procedure except they return a single value a single value
- 21. Triggers Triggers Associated with a particular table Associated with a particular table Automatically executed when a Automatically executed when a particular event occurs particular event occurs • Insert Insert • Update Update • Delete Delete • Others Others
- 22. Triggers vs. Procedures Triggers vs. Procedures Procedures are Procedures are explicitly explicitly executed by executed by a user or application a user or application Triggers are Triggers are implicitly implicitly executed executed (fired) when the triggering event (fired) when the triggering event occurs occurs Triggers should not be used as a lazy Triggers should not be used as a lazy way to invoke a procedure as they way to invoke a procedure as they are fired are fired every every time the event occurs time the event occurs
- 24. Triggers Triggers The The trigger specification trigger specification names the names the trigger and indicates when it will fire trigger and indicates when it will fire The The trigger body trigger body contains the PL/SQL contains the PL/SQL code to accomplish whatever task(s) code to accomplish whatever task(s) need to be performed need to be performed
- 26. Triggers Timing Triggers Timing A triggers timing has to be specified A triggers timing has to be specified first first • Before (most common) Before (most common) Trigger should be fired before the operation Trigger should be fired before the operation • i.e. before an insert i.e. before an insert • After After Trigger should be fired after the operation Trigger should be fired after the operation • i.e. after a delete is performed i.e. after a delete is performed
- 27. Trigger Events Trigger Events Three types of events are available Three types of events are available • DML events DML events • DDL events DDL events • Database events Database events
- 28. DML Events DML Events Changes to data in a table Changes to data in a table • Insert Insert • Update Update • Delete Delete
- 29. DDL Events DDL Events Changes to the definition of objects Changes to the definition of objects • Tables Tables • Indexes Indexes • Procedures Procedures • Functions Functions • Others Others Include CREATE, ALTER and DROP Include CREATE, ALTER and DROP statements on these objects statements on these objects
- 30. Database Events Database Events Server Errors Server Errors Users Log On or Off Users Log On or Off Database Started or Stopped Database Started or Stopped
- 31. Trigger DML Events Trigger DML Events Can specify one or more events in Can specify one or more events in the specification the specification • i.e. INSERT OR UPDATE OR DELETE i.e. INSERT OR UPDATE OR DELETE Can specify one or more columns to Can specify one or more columns to be associated with a type of event be associated with a type of event • i.e. BEFORE UPDATE OF SID OR SNAME i.e. BEFORE UPDATE OF SID OR SNAME
- 32. Table Name Table Name The next item in the trigger is the The next item in the trigger is the name of the table to be affected name of the table to be affected
- 33. Trigger Level Trigger Level Two levels for Triggers Two levels for Triggers • Row-level trigger Row-level trigger Requires FOR EACH ROW clause Requires FOR EACH ROW clause • If operation affects multiple rows, trigger fires If operation affects multiple rows, trigger fires once for each row affected once for each row affected • Statement-level trigger Statement-level trigger • DML triggers should be row-level DML triggers should be row-level • DDL and Database triggers should not DDL and Database triggers should not be row-level be row-level
- 35. Triggers Triggers Conditions Available So Multiple Conditions Available So Multiple Operations Can Be Dealt With In Operations Can Be Dealt With In Same Trigger Same Trigger • Inserting, Updating, Deleting Inserting, Updating, Deleting Column Prefixes Allow Identification Column Prefixes Allow Identification Of Value Changes Of Value Changes • New, Old New, Old
- 36. Triggers Exceptions Triggers Exceptions EXCEPTION Data Type Allows EXCEPTION Data Type Allows Custom Exceptions Custom Exceptions RAISE Allows An Exception To Be RAISE Allows An Exception To Be Manually Occur Manually Occur RAISE_APPLICATION_ERROR Allows RAISE_APPLICATION_ERROR Allows Termination Using A Custom Error Termination Using A Custom Error Message Message • Must Be Between -20000 and -20999 Must Be Between -20000 and -20999 • Message Can Be Up to 512 Bytes Message Can Be Up to 512 Bytes
- 37. Cursors Cursors Cursors Hold Result of an SQL Cursors Hold Result of an SQL Statement Statement Two Types of Cursors in PL/SQL Two Types of Cursors in PL/SQL • Implicit – Automatically Created When a Implicit – Automatically Created When a Query or Manipulation is for a Single Query or Manipulation is for a Single Row Row • Explicit – Must Be Declared by the User Explicit – Must Be Declared by the User Creates a Unit of Storage Called a Result Set Creates a Unit of Storage Called a Result Set
- 38. Cursors Cursors Result Set Result Set MIS380 MIS380 DATABASE DESIGN DATABASE DESIGN 4 4 MIS202 MIS202 INFORMATION SYSTEMS INFORMATION SYSTEMS 3 3 <Cursor <Cursor MIS485 MIS485 MANAGING TECHNOLOGY MANAGING TECHNOLOGY 4 4 MIS480 MIS480 ADVANCED DATABASE ADVANCED DATABASE 4 4
- 39. Cursors Cursors Declaring an Explicit Cursor Declaring an Explicit Cursor CURSOR CursorName IS SelectStatement; CURSOR CursorName IS SelectStatement; Opening an Explicit Cursor Opening an Explicit Cursor OPEN CursorName; OPEN CursorName; Accessing Rows from an Explicit Accessing Rows from an Explicit Cursor Cursor FETCH CursorName INTO RowVariables; FETCH CursorName INTO RowVariables;
- 40. Cursors Cursors Declaring Variables of the Proper Declaring Variables of the Proper Type with %TYPE Type with %TYPE VarName TableName.FieldName%TYPE; VarName TableName.FieldName%TYPE; Declaring Variables to Hold An Entire Declaring Variables to Hold An Entire Row Row VarName CursorName%ROWTYPE; VarName CursorName%ROWTYPE; Releasing the Storage Area Used by Releasing the Storage Area Used by an Explicit Cursor an Explicit Cursor CLOSE CursorName; CLOSE CursorName;
- 41. Iterative Structures Iterative Structures LOOP … EXIT … END LOOP LOOP … EXIT … END LOOP • EXIT with an If Avoids Infinite Loop EXIT with an If Avoids Infinite Loop LOOP … EXIT WHEN … END LOOP LOOP … EXIT WHEN … END LOOP • Do Not Need An If to Control EXIT Do Not Need An If to Control EXIT WHILE … LOOP … END LOOP WHILE … LOOP … END LOOP • Eliminates Need for EXIT Eliminates Need for EXIT FOR … IN … END LOOP FOR … IN … END LOOP • Eliminates Need for Initialization of Eliminates Need for Initialization of Counter Counter
- 42. Cursor Control With Loops Cursor Control With Loops Need a Way to Fetch Repetitively Need a Way to Fetch Repetitively Need a Way to Determine How Many Need a Way to Determine How Many Rows to Process With a Cursor Rows to Process With a Cursor • Cursor Attributes Cursor Attributes CursorName%ROWCOUNT – Number of CursorName%ROWCOUNT – Number of Rows in a Result Set Rows in a Result Set CursorName%FOUND – True if a Fetch CursorName%FOUND – True if a Fetch Returns a Row Returns a Row CursorName%NOTFOUND – True if CursorName%NOTFOUND – True if Fetch Goes Past Last Row Fetch Goes Past Last Row
- 43. Cursor For Loop Cursor For Loop Processing an Entire Result Set Processing an Entire Result Set Common Common Special Form of FOR … IN to Manage Special Form of FOR … IN to Manage Cursors Cursors No Need for Separate OPEN, FETCH No Need for Separate OPEN, FETCH and CLOSE statements and CLOSE statements Requires %ROWTYPE Variable Requires %ROWTYPE Variable