Creating Functions

Overview of Stored Functions A function is a named PL/SQL block that returns a value. A function is a named PL/SQL block that returns a value. A function can be stored in the database, as a database object, for repeated execution. A function can be stored in the database, as a database object, for repeated execution. A function can be called as part of an expression. A function can be called as part of an expression. A function is a named PL/SQL block that returns a value. A function is a named PL/SQL block that returns a value. A function can be stored in the database, as a database object, for repeated execution. A function can be stored in the database, as a database object, for repeated execution. A function can be called as part of an expression. A function can be called as part of an expression.

Syntax for Creating Functions CREATE [OR REPLACE] FUNCTION function_name (argument1 [mode1] datatype1, argument2 [mode2] datatype2,... RETURN datatype IS|AS PL/SQL Block; CREATE [OR REPLACE] FUNCTION function_name (argument1 [mode1] datatype1, argument2 [mode2] datatype2,... RETURN datatype IS|AS PL/SQL Block;

Creating a Stored Function Using SQL*Plus  1.Enter the text of the CREATE FUNCTION statement in a system editor or word processor and save it as a script file (.sql extension).  2.From SQL*Plus, run the script file to compile the source code into p- code and store both in the database.  1.Enter the text of the CREATE FUNCTION statement in a system editor or word processor and save it as a script file (.sql extension).  2.From SQL*Plus, run the script file to compile the source code into p- code and store both in the database. 3.Invoke the function from an Oracle Server environment to determine whether it executes without error.

Creating a Stored Function Using SQL*Plus: Example SQL> CREATE OR REPLACE FUNCTION get_sal 2 (v_id IN emp.empno%TYPE) 3 RETURN NUMBER 4 IS 5 v_salaryemp.sal%TYPE :=0; 6 BEGIN 7 SELECT sal 8 INTO v_salary 9 FROM emp 10 WHERE empno = v_id; 11 RETURN (v_salary); 12 END get_sal; 13 / SQL> CREATE OR REPLACE FUNCTION get_sal 2 (v_id IN emp.empno%TYPE) 3 RETURN NUMBER 4 IS 5 v_salaryemp.sal%TYPE :=0; 6 BEGIN 7 SELECT sal 8 INTO v_salary 9 FROM emp 10 WHERE empno = v_id; 11 RETURN (v_salary); 12 END get_sal; 13 /

Executing Functions Invoke a function as part of a PL/SQL expression. Invoke a function as part of a PL/SQL expression. Create a host variable to hold the returned value. Create a host variable to hold the returned value. Execute the function. The host variable will be populated by the RETURN value. Execute the function. The host variable will be populated by the RETURN value. Invoke a function as part of a PL/SQL expression. Invoke a function as part of a PL/SQL expression. Create a host variable to hold the returned value. Create a host variable to hold the returned value. Execute the function. The host variable will be populated by the RETURN value. Execute the function. The host variable will be populated by the RETURN value.

Advantages of User-Defined Functions in SQL Expressions Extend SQL where activities are too complex, too awkward, or unavailable with SQL Extend SQL where activities are too complex, too awkward, or unavailable with SQL Query efficiency: functions used in the WHERE clause can filter data Query efficiency: functions used in the WHERE clause can filter data Manipulate character strings Manipulate character strings Provide parallel query execution Provide parallel query execution Extend SQL where activities are too complex, too awkward, or unavailable with SQL Extend SQL where activities are too complex, too awkward, or unavailable with SQL Query efficiency: functions used in the WHERE clause can filter data Query efficiency: functions used in the WHERE clause can filter data Manipulate character strings Manipulate character strings Provide parallel query execution Provide parallel query execution

Removing Functions Using SQL*Plus: Using SQL*Plus: Drop a server-side function. Using Procedure Builder: Using Procedure Builder: Drop a server-side function.Drop a server-side function. Drop a client-side function.Drop a client-side function. Using SQL*Plus: Using SQL*Plus: Drop a server-side function. Using Procedure Builder: Using Procedure Builder: Drop a server-side function.Drop a server-side function. Drop a client-side function.Drop a client-side function.

Removing a Server-Side Function  Using SQL*Plus Syntax Syntax Example Example  Using SQL*Plus Syntax Syntax Example Example SQL> DROP FUNCTION get_salary; Function dropped. SQL> DROP FUNCTION get_salary; Function dropped. DROP FUNCTION function_name

Procedure or Function? Procedure(DECLARE)BEGINEXCEPTIONEND; IN argument OUT argument IN OUT argument CallingEnvironment CallingEnvironmentFunction(DECLARE)BEGINEXCEPTIONEND; IN argument

Comparing Procedures and Functions Procedure Execute as a PL/SQL statement No RETURN datatype Can return one or more values Function Invoke as part of an expression Must contain a RETURN datatype Must return a value

Benefits of Stored Procedures and Functions Improved performance Improved performance Improved maintenance Improved maintenance Improved data security and integrity Improved data security and integrity Improved performance Improved performance Improved maintenance Improved maintenance Improved data security and integrity Improved data security and integrity

Creating Packages

Overview of Packages Group logically related PL/SQL types, items, and subprograms Group logically related PL/SQL types, items, and subprograms Consist of two parts: Consist of two parts: SpecificationSpecification BodyBody Cannot be called, parameterized, or nested Cannot be called, parameterized, or nested Allow Oracle8 to read multiple objects into memory at once Allow Oracle8 to read multiple objects into memory at once Group logically related PL/SQL types, items, and subprograms Group logically related PL/SQL types, items, and subprograms Consist of two parts: Consist of two parts: SpecificationSpecification BodyBody Cannot be called, parameterized, or nested Cannot be called, parameterized, or nested Allow Oracle8 to read multiple objects into memory at once Allow Oracle8 to read multiple objects into memory at once

Advantages of Packages Modularity Modularity Easier application design Easier application design Information hiding Information hiding Added functionality Added functionality Better performance Better performance Overloading Overloading Modularity Modularity Easier application design Easier application design Information hiding Information hiding Added functionality Added functionality Better performance Better performance Overloading Overloading

Developing a Package Procedure A declaration Procedure B definition Packagespecification Packagebody Procedure A definition 5

Developing a Package Procedure A declaration Procedure B definition Packagespecification Packagebody Procedure A definition 5

Developing a Package Text file Source code p-code Edit Store in database Compile 1 2 System Editor ProcedureBuilder Invoke

Developing a Package Saving the text of the CREATE PACKAGE statement in two different text files facilitates later modifications to the package. Saving the text of the CREATE PACKAGE statement in two different text files facilitates later modifications to the package. A package specification can exist without a package body, but a package body cannot exist without a package specification. A package specification can exist without a package body, but a package body cannot exist without a package specification. If you have incorporated a standalone procedure into a package, you should drop your standalone procedure. If you have incorporated a standalone procedure into a package, you should drop your standalone procedure. Saving the text of the CREATE PACKAGE statement in two different text files facilitates later modifications to the package. Saving the text of the CREATE PACKAGE statement in two different text files facilitates later modifications to the package. A package specification can exist without a package body, but a package body cannot exist without a package specification. A package specification can exist without a package body, but a package body cannot exist without a package specification. If you have incorporated a standalone procedure into a package, you should drop your standalone procedure. If you have incorporated a standalone procedure into a package, you should drop your standalone procedure.

CREATE [OR REPLACE] PACKAGE package_name IS | AS public type and item declarations subprogram specifications END package_name; CREATE [OR REPLACE] PACKAGE package_name IS | AS public type and item declarations subprogram specifications END package_name; Creating the Package Specification SyntaxSyntax

COMM_PACKAGE package G_COMM RESET_COMM procedure declaration Packagespecification 1 2 Declaring Public Constructs

Creating a Package Specification: Example SQL>CREATE OR REPLACE PACKAGE comm_package IS 2 g_comm NUMBER := 10; --initialized to 10 3 PROCEDURE reset_comm 4 (v_comm INNUMBER); 5 END comm_package; 6 /

Declaring a Global Variable or a Public Procedure SQL>EXECUTE comm_package.g_comm := 5 SQL>EXECUTE comm_package.reset_comm(8)

Creating the Package Body SyntaxSyntax CREATE [OR REPLACE] PACKAGE BODY package_name IS | AS private type and item declarations subprogram bodies END package_name; CREATE [OR REPLACE] PACKAGE BODY package_name IS | AS private type and item declarations subprogram bodies END package_name;

G_COMM RESET_COMM procedure declaration VALIDATE_COMM function definition Packagespecification Packagebody RESET_COMM procedure definition COMM_PACKAGE package Public and Private Constructs

Creating a Package Body: Example SQL>CREATE OR REPLACE PACKAGE BODY comm_package IS 2 FUNCTION validate_comm 3 (v_comm IN NUMBER) RETURN BOOLEAN 4 IS 5 v_max_comm NUMBER; 6 BEGIN 7 SELECT MAX(comm) 8 INTO v_max_comm 9 FROM emp; 10 IF v_comm > v_max_comm THEN RETURN(FALSE); 11 ELSE RETURN(TRUE); 12 END IF; 13 END validate_comm; 14 END comm_package; 15 /

SQL>PROCEDURE reset_comm 2 (v_comm IN NUMBER) 3 IS 4 v_validBOOLEAN; 5 BEGIN 6 v_valid := validate_comm(v_comm); 7 IF v_valid = TRUE THEN 8 g_comm := v_comm; 9 ELSE 10 RAISE_APPLICATION_ERROR 11(-20210,'Invalid commission'); 12 END IF; 13 END reset_comm; 14 END comm_package; 15 / Creating a Package Body: Example

Invoking Package Constructs  Example 1: Invoke a function from a procedure within the same package. CREATE OR REPLACE PACKAGE BODY comm_package IS... PROCEDURE reset_comm(v_comm IN NUMBER) IS v_validBOOLEAN; BEGIN v_valid := validate_comm(v_comm); IF v_valid = TRUE THEN g_comm := v_comm; ELSE RAISE_APPLICATION_ERROR (-20210, 'Invalid comm'); END IF; END reset_comm; END comm_package;

 Example 2: Invoke a package procedure from SQL*Plus.  Example 3: Invoke a package procedure in a different schema.  Example 4: Invoke a package procedure in a remote database.  Example 2: Invoke a package procedure from SQL*Plus.  Example 3: Invoke a package procedure in a different schema.  Example 4: Invoke a package procedure in a remote database. Invoking Package Constructs SQL>EXECUTE comm_package.reset_comm(1500); SQL>EXECUTE scott.comm_package.reset_comm(1500); SQL>EXECUTE (1500);

Referencing a Global Variable Within the Package Example 1 CREATE OR REPLACE PACKAGE BODY comm_package IS... PROCEDURE reset_comm(v_comm IN NUMBER) IS v_validBOOLEAN; BEGIN v_valid := validate_comm(v_comm); IF v_valid = TRUE THEN g_comm := v_comm; ELSE RAISE_APPLICATION_ERROR (-20210,'Invalid comm'); END IF; END reset_comm; END comm_package;

DROP PACKAGE package_name Removing Packages To remove the package specification and the body: To remove the package body: DROP PACKAGE BODY package_name

SummarySummary A function is a named PL/SQL block that must return a value. A function is a named PL/SQL block that must return a value. A function is invoked as part of an expression. A function is invoked as part of an expression. A stored function can be called in SQL statements. A stored function can be called in SQL statements. A function is a named PL/SQL block that must return a value. A function is a named PL/SQL block that must return a value. A function is invoked as part of an expression. A function is invoked as part of an expression. A stored function can be called in SQL statements. A stored function can be called in SQL statements.

SummarySummary Improve organization, management, security, and performance. Improve organization, management, security, and performance. Group related procedures and functions together. Group related procedures and functions together. Change a package body without affecting a package specification. Change a package body without affecting a package specification. Grant security access to the entire package. Grant security access to the entire package. Improve organization, management, security, and performance. Improve organization, management, security, and performance. Group related procedures and functions together. Group related procedures and functions together. Change a package body without affecting a package specification. Change a package body without affecting a package specification. Grant security access to the entire package. Grant security access to the entire package.