pl/sql Procedure

pl/sql Procedure

• 1.
  Prof. Neeraj Bhargava PoojaDixit Department of Computer Science School of Engineering & System Science MDS, University Ajmer, Rajasthan, India 1
• 2.
   Procedures arenamed PL/SQL blocks.  Created/owned by a particular schema  Privilege to execute a specific procedure can be granted to or revoked from application users in order to control data access.  Requires CREATE PROCEDURE (to create in your schema) or CREATE ANY PROCEDURE privilege (to create in other schemas). 2
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  CREATE [OR REPLACE]PROCEDURE <procedure_name> (<parameter1_name> <mode> <data type>, <parameter2_name> <mode> <data type>, ...) {AS|IS} <Variable declarations> BEGIN Executable statements [EXCEPTION Exception handlers] END <optional procedure name>;  Unique procedure name is required.  OR REPLACE clause facilitates testing.  Parameters are optional – enclosed in parentheses when used.  AS or IS keyword is used – both work identically.  Procedure variables are declared prior to the BEGIN keyword.  DECLARE keyword is NOT used in named procedure. 3
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   To Compile/Loada procedure use either the “@” symbol or the START SQL command to compile the file. The <SQL filename> parameter is the .sql file that contains the procedure to be compiled. SQL>@<SQL filename> SQL>start <SQL filename>  Filename does not need to be the same as the procedure name. The .sql file only contains the procedure code.  Compiled procedure is stored in the database, not the .sql file.  Use SHOW ERRORS command if the procedure does not compile without errors. Use EXECUTE to run procedure. SQL> show errors; SQL> EXECUTE Insert_Employee 4
• 5.
   Both proceduresand functions can take parameters.  Values passed as parameters to a procedure as arguments in a calling statement are termed actual parameters.  The parameters in a procedure declaration are called formal parameters.  The values stored in actual parameters are values passed to the formal parameters – the formal parameters are like placeholders to store the incoming values.  When a procedure completes, the actual parameters are assigned the values of the formal parameters.  A formal parameter can have one of three possible modes: (1) IN, (2), OUT, or (3) IN OUT. 5
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   IN –this parameter type is passed to a procedure as a read-only value that cannot be changed within the procedure – this is the default mode.  OUT – this parameter type is write-only, and can only appear on the left side of an assignment statement in the procedure – it is assigned an initial value of NULL.  IN OUT – this parameter type combines both IN and OUT; a parameter of this mode is passed to a procedure, and its value can be changed within the procedure.  If a procedure raises an exception, the formal parameter values are not copied back to their corresponding actual parameters. 6
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   Procedures donot allow specifying a constraint on the parameter data type.  Example: the following CREATE PROCEDURE statement is not allowed because of the specification that constrains the v_Variable parameter to NUMBER(2). Instead use the general data type of NUMBER. /* Invalid constraint on parameter. */ CREATE OR REPLACE PROCEDURE proSample (v_Variable NUMBER(2), ...) /* Valid parameter. */ CREATE OR REPLACE PROCEDURE proSample (v_Variable NUMBER, ...) 7
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  CREATE OR REPLACEPROCEDURE DisplaySalary IS -- create local variable with required constraint temp_Salary NUMBER(10,2); BEGIN SELECT Salary INTO temp_Salary FROM Employee WHERE EmployeeID = '01885'; IF temp_Salary > 15000 THEN DBMS_OUTPUT.PUT_LINE ('Salary > 15,000.'); ELSE DBMS_OUTPUT.PUT_LINE ('Salary < 15,000.'); END IF; EXCEPTION WHEN NO_DATA_FOUND THEN DBMS_OUTPUT.PUT_LINE ('Employee not found.'); END DisplaySalary; / 8
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  SQL> exec DisplaySalary Salary> 15,000. PL/SQL procedure successfully completed. 9
• 10.
  CREATE OR REPLACEPROCEDURE DisplaySalary2(p_EmployeeID IN CHAR, p_Salary OUT NUMBER) IS v_Salary NUMBER(10,2); BEGIN SELECT Salary INTO v_Salary FROM Employee WHERE EmployeeID = p_EmployeeID; IF v_Salary > 15000 THEN DBMS_OUTPUT.PUT_LINE ('Salary > 15,000.'); ELSE DBMS_OUTPUT.PUT_LINE ('Salary <= 15,000.'); END IF; p_Salary := v_Salary; EXCEPTION WHEN NO_DATA_FOUND THEN DBMS_OUTPUT.PUT_LINE ('Employee not found.'); END DisplaySalary2; 10
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  DECLARE v_SalaryOutput NUMBER :=0; BEGIN -- call the procedure DisplaySalary2('01885', v_SalaryOutput); -- display value of salary after the call DBMS_OUTPUT.PUT_LINE ('Actual salary: ' ||TO_CHAR(v_SalaryOutput)); END; / Salary > 15,000. Actual salary: 16250 PL/SQL procedure successfully completed. 11
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   The SQLstatement to drop a procedure is the straight-forward DROP PROCEDURE <procedureName> command.  This is a data definition language (DDL) command, and so an implicit commit executes prior to and immediately after the command. SQL> DROP PROCEDURE DisplaySalary2; Procedure dropped. 12