Procedure & Function

Transcription

1 The Islamic University of Gaza Faculty of Engineering Dept. of Computer Engineering Database Lab (ECOM 4113) Lab 8 Procedure & Function Eng. Ibraheem Lubbad

2 PL/SQL has two types of subprograms called procedures and functions. Generally, you use a procedure to perform an action and a function to compute a value. Procedures A procedure is a type of subprogram that performs an action. It can be stored in the database as a schema object for repeated execution CREATE [OR REPLACE] PROCEDURE PROCEDURE_NAME [(PARAMETER1 [MODE] DATATYPE1, PARAMETER2 [MODE] DATATYPE2,...)] IS AS [local declarations] The syntax of procedure executable statements [EXCEPTION exception handlers] END [PROCEDURE_NAME]; PARAMETER1 represents the name of a parameter. The mode option defines how a parameter is used: IN (default), OUT, or IN OUT. DATATYPE1 specifies the parameter data type, WITHOUT any precision. : CREATE OR REPLACE PROCEDURE RAISE_SALARY IS UPDATE INSTRUCTOR $RNI3LTZ.asd SET SALARY=SALARY+(SALARY * 10/100) WHERE ID=10101; To Call procedure use EXECUTE keyword EXECUTE raise_salary();

3 : Using in mode: These types of parameters are used to send values to stored procedures. Using in mode CREATE OR REPLACE PROCEDURE RAISE_SALARY(INST_ID INSTRUCTOR.ID%TYPE, PERCENT NUMBER) IS $RNI3LTZ.asd UPDATE INSTRUCTOR SET SALARY=SALARY+(SALARY *PERCENT/100) WHERE ID=INST_ID; EXECUTE raise_salary(10101,10); The procedure can also be called from another PL/SQL block: RAISE_SALARY (10101,10); To check the effects of executing procedure, check the salary before and after execution. Using in mode DECLARE SAL instructor. SALARY%TYPE; SELECT SALARY INTO SAL FROM instructor WHERE id = 10101; DBMS_OUTPUT. PUT_LINE('SALARY BEFORE EXECUTING PROCEDURE: ' SAL); RAISE_SALARY (10101, 10); SELECT SALARY INTO SAL FROM instructor WHERE id = 10101; DBMS_OUTPUT. PUT_LINE('SALARY AFTER EXECUTING PROCEDURE: ' SAL);

4 : Using Out Mode: These types of parameters are used to get values from stored procedures Using out mode CREATE OR REPLACE PROCEDURE STUDENT_INFO (STD_ID IN STUDENT.ID%TYPE, STD_NAME OUT STUDENT.NAME%TYPE, STD_DEPT OUT STUDENT.DEPT_NAME%TYPE)IS SELECT NAME, DEPT_NAME INTO STD_NAME,STD_DEPT FROM STUDENT WHERE ID=STD_ID; Using out mode DECLARE STD_NAME STUDENT. NAME%TYPE; STD_DEPT STUDENT.DEPT_NAME%TYPE; STUDENT_INFO( 12345, STD_NAME, STD_DEPT); DBMS_OUTPUT. PUT_LINE('STDUENT NAME : ' STD_NAME); DBMS_OUTPUT. PUT_LINE('DEPARTMENT NAME : ' STD_DEPT); Note :The actual parameter that corresponds to an OUT or IN OUT formal parameter must be a variable; it cannot be a constant or an expression, so you have to pass variable to Std_name and std_dept attributes.

5 : Using IN OUT Mode: An IN OUT parameter passes initial values to a subprogram and returns updated values to the caller. It can be assigned a value and its value can be read. IN OUT formal parameter must be a variable, it cannot be a constant or an expression. Using in out mode CREATE OR REPLACE PROCEDURE COUNT_INST_DEPT (PARAM IN OUT VARCHAR2) IS SELECT COUNT(*) INTO PARAM FROM INSTRUCTOR WHERE DEPT_NAME = PARAM ; Using in out mode DECLARE PARAM VARCHAR2(20):='Comp. Sci.'; DBMS_OUTPUT.PUT_LINE('DEPARTMENT NAME : ' PARAM); COUNT_INST_DEPT(PARAM); DBMS_OUTPUT.PUT_LINE('NUMBER OF INSTRUCTOR : ' PARAM);

6 Functions: A function is a subprogram that computes a value. Functions and procedures are structured alike, except that functions have a RETURN clause. It is called as part of an expression or is used to provide a parameter value. CREATE [OR REPLACE] FUNCTION FUNCTION_NAME [(PARAMETER1 DATATYPE1, PARAMETER2 DATATYPE2,...)] RETURN DATATYPE IS AS [ local declarations ] executable statements [ EXCEPTION exception handlers ] END [FUNCTION_NAME]; : CREATE OR REPLACE FUNCTION FORMAT_SALARY (SAL IN INSTRUCTOR.SALARY%TYPE) RETURN VARCHAR2 IS TEMP VARCHAR2 (20):=''; TEMP := TO_CHAR(SAL, '$999,999.00'); RETURN TEMP; Then use it as a build-in function: Use user define function SELECT NAME, SALARY, FORMAT_SALARY(SALARY) FROM INSTRUCTOR;

7 : Create function that, returns the count of the number of instructors in that department for given the name of a department. CREATE OR REPLACE FUNCTION DEPT_COUNT_INST (DEPT IN INSTRUCTOR.DEPT_NAME%TYPE) RETURN NUMBER IS C_INST NUMBER (2); SELECT COUNT(ID) INTO C_INST FROM INSTRUCTOR WHERE DEPT_NAME= DEPT; RETURN C_INST; END DEPT_COUNT_INST; This function can b used it in a query that returns names, budgets and of all departments with more than 12 instructors SELECT DEPT_NAME,BUDGET,BUILDING FROM DEPARTMENT WHERE DEPT_COUNT_INST(DEPT_NAME)>=2; Using OUT in function: Using out mode CREATE OR REPLACE FUNCTION DEPT_INFO (DEPT IN VARCHAR2, DEPT_BUILDING OUT VARCHAR2)RETURN NUMBER IS COUNT_INS NUMBER(2); SELECT BUILDING INTO DEPT_BUILDING FROM DEPARTMENT WHERE DEPT_NAME = DEPT; SELECT COUNT(*) INTO COUNT_INS FROM INSTRUCTOR WHERE DEPT_NAME = DEPT; RETURN COUNT_INS;

8 Note: in this case we cannot use function in sql statement but we can use it just in PL/SQL Block. Using out mode DECLARE D_BUILDING DEPARTMENT.BUILDING%TYPE; C_INST NUMBER(2):=0; C_INST:=DEPT_INFO( 'Comp. Sci.', D_BUILDING); DBMS_OUTPUT.PUT_LINE('DEPARTMENT NAME : COMP. SCI.'); DBMS_OUTPUT.PUT_LINE('NUMBER OF INSTRUCTOR :' C_INST); DBMS_OUTPUT.PUT_LINE('DEPARTMENT BULDING :' D_BUILDING); Using IN OUT in function: Using in out mode CREATE OR REPLACE FUNCTION DEPT_INFO (PARAM IN OUT VARCHAR2 )RETURN NUMBER IS COUNT_INS NUMBER(2); SELECT COUNT(*) INTO COUNT_INS FROM INSTRUCTOR WHERE DEPT_NAME = PARAM; SELECT BUILDING INTO PARAM FROM DEPARTMENT WHERE DEPT_NAME = PARAM; RETURN COUNT_INS;

9 Using in out mode DECLARE PARAM VARCHAR2(20):='Comp. Sci.'; C_INST NUMBER(2):=0; C_INST:=DEPT_INFO(PARAM); DBMS_OUTPUT.PUT_LINE('DEPARTMENT NAME : COMP. SCI.'); DBMS_OUTPUT.PUT_LINE('NUMBER OF INSTRUCTOR :' C_INST); DBMS_OUTPUT.PUT_LINE('DEPARTMENT BULDING :' PARAM); : Create registerstudent function to registers a student after ensuring classroom is not exceeded, returns 0 when success, and -1 if capacity is exceeded. CREATE OR REPLACE FUNCTION REGISTERSTUDENT (S_ID IN TAKES.ID%TYPE,S_COURSE_ID IN TAKES.COURSE_ID%TYPE,S_SEC_ID IN TAKES.SEC_ID%TYPE, S_SEMESTER IN TAKES.SEMESTER%TYPE, S_YEAR IN TAKES.YEAR%TYPE, MSG OUT VARCHAR2) RETURN NUMBER IS LIMIT_NUM NUMBER(2); CURR_NUM NUMBER(2); SELECT CAPACITY INTO LIMIT_NUM FROM CLASSROOM NATURAL JOIN SECTION WHERE COURSE_ID=S_COURSE_ID AND SEC_ID=S_SEC_ID AND SEMESTER=S_SEMESTER AND YEAR = S_YEAR; SELECT COUNT(*) INTO CURR_NUM FROM TAKES WHERE COURSE_ID=S_COURSE_ID AND SEC_ID=S_SEC_ID AND SEMESTER=S_SEMESTER AND YEAR = S_YEAR; IF CURR_NUM < LIMIT_NUM THEN INSERT INTO TAKES (ID, COURSE_ID,SEC_ID,SEMESTER,YEAR ) VALUES (S_ID,S_COURSE_ID,S_SEC_ID,S_SEMESTER,S_YEAR); MSG :='DONE.. ' S_COURSE_ID ' ' S_SEC_ID ' ' LIMIT_NUM; RETURN 0; ELSE MSG :='ENROLLMENT LIMIT REACHED FOR COURSE ' S_COURSE_ID ' ' S_SEC_ID ' ' LIMIT_NUM; RETURN -1; END IF ;

10 Viewing Procedures/Functions in the Data Dictionary Information for PL/SQL procedures is saved in the following data dictionary views: USER_SOURCE: to view the subprograms that you own. ALL_SOURCE: to view the procedures that are owned by others who have granted you the EXECUTE privilege. SELECT * FROM USER_SOURCE; To view the code for a specific procedure/function, select TEXT Column only, and specify the Capital latter name of procedure/function in where clause SELECT TEXT FROM USER_SOURCE WHERE NAME= 'DEPT_INFO'; As any a schema object we can delete subprograms using drop statement. DROP FUNCTION DEPT_INFO; END