PL/SQL ISYS 464

PL/SQL Block-Structured Variable declaration section Executable section Exception-handling section

Variable Declaration Variable name: begin with a letter and up to 30 characters. Data types: –Character: CHAR(n), VARCHAR2(n) –Number: INTEGER, INT, SMALLINT –DECIMAL(i,j), NUMBER(i,j) –Boolean –Date

Examples DECLARE EidCHAR(3); EnameVARCHAR2(25); HireDateDATE DEFAULT SYSDATE; SalaryNUMBER(7,2) TaxRateNUMBER(4,2) :=5.25

%TYPE Use a column’s data type as the data type for the variable: –CustomerName Customer.Cname%TYPE;

Executable Section BEGIN –Statements END; / –“/ “ signals the end of program.

Assignment Statement Tax := Salary * TaxRate Arithemetic operators: –+, -, *, /, ** Concatenation: –|| FullName := (FirstName || ‘ ‘ || LastName);

Substitution Variables &variableName –Ex. &Salary On screen you will see: –Enter value for Salary: Select * from Customer Where CID=‘&CID’; Ex1: Get input from screen: –Salary := &Salary;

SELECT … INTO SELECT columns separated by commas INTO variables separated by commas FROM tablename WHERE condition; Ex1: –SELECT cid, cname INTO custID, customername –FROM customer –WHERE cid = ‘c01’; Ex2: Using substituion variable –SELECT cid, cname INTO custID, customername –FROM customer –WHERE cid = ‘&cid’;

Decisions IF condition THEN –Statements/* each statement ends with ; */ END IF; IF … THEN … ELSE …END IF; IF … THEN ELSIF ……ELSE … END IF;

Loop WHILE condition LOOP –Statements END LOOP; FOR i IN LOOP –Statements END LOOP

Printing SET SERVEROUTPUT ON; DBMS_OUTPUT.PUT_LINE(string to print); –DBMS_OUTPUT is a build in package, PUT_LINE is a procedure in that package. Ex. –Tax:=Salary * TaxRate; –DBMS_OUTPUT.PUT_LINE(‘Your tax is: ‘ || Tax);

Caltax.sql declare taxRate number(3,2); eid emp.empid%type; empSalary emp.salary%type; tax number(7,2); begin taxRate :=&taxRate; select salary into empSalary from emp where empid = '&eid'; tax := empSalary * taxRate; dbms_output.put_line('Tax is : ' || tax); end; /

Exceptions Exceptions are errors. Predefined exceptions: –No_Data_Found: Select statement returns no row. –Too_Many_Rows: Single-Row Select statement returns more than one row. –Value_Error:Data conversion errors.

Handling Exceptions Exception –WHEN exceptionname THEN –Statements –WHEN OTHERS THEN –Statements Ex: PLSQLException.SQL Declare CustName Customer.Cname%Type; begin select Cname into Custname from customer where cid='&CID'; dbms_output.put_line('Customer name is : ' || Custname); exception when no_data_found then dbms_output.put_line('Customer record not exist'); end; /

Creating Stored Procedure A procedure is a named program block: CREATE [OR REPLACE] PROCEDURE procedurename IS [Variable declarations] BEGIN Statements END; / Note: To run a procedure: EXECUTE procedurename

create or replace procedure addorder ( ordid orders.oid%TYPE, custID orders.cid%TYPE, salesID orders.sid%TYPE, orddate orders.odate%TYPE) is tempid customers.cid%TYPE; begin select cid into tempid from customers where cid=custid; insert into orders values(ordid,custid,salesid,orddate); exception when no_data_found then dbms_output.put_line('Customer record not exist'); end; / Note: To run a stored procedure: execute addorder('O8','C1','S3','05-NOV-07');

Functions CREATE [OR REPLACE] FUNCTION functionname IS [Variable declarations] BEGIN Statements RETURN expression; END; /

create or replace function emptax(sal emp.salary%type) return number is tax number(6,2); begin if sal < then tax:=sal*0.1; elsif sal < then tax:=sal*0.2; else tax:=sal*0.3; end if; return tax; end; /

Using the User-defined Function with SQL SELECT empid, ename, emptax(salary) FROM emp;

Cursors A cursor is a pointer to a set of records returned by a SQL statement. It enables you to take a set of records and deal with it on a row-by-row basis.

Defining and Using Cursors Declare cursor: –CURSOR cursorname IS SQL statement Ex: cursor maleemp is select empid,ename,salary from emp where sex='M'; Open cursor: OPEN maleemp; Fetch data into variables: FETCH maleemp into eid,empname,sal; Use %FOUND to test if record exist CLOSE cursor

declare eid emp.empid%type; empname emp.ename%type; sal emp.salary%type; cursor maleemp is select empid,ename,salary from emp where sex='M'; begin open maleemp; fetch maleemp into eid,empname,sal; while maleemp%found loop dbms_output.put_line(eid || empname || sal); fetch maleemp into eid,empname,sal; end loop; close maleemp; end; / Note: To run a cursor: SQL> Start C:\Empcursor1.sql

Cursor with Arguments declare eid emp.empid%type; empname emp.ename%type; sal emp.salary%type; cursor gender(s emp.sex%type) is select empid,ename,salary from emp where sex=s; begin open gender('&gender'); fetch gender into eid,empname,sal; while gender%found loop dbms_output.put_line(eid || empname || sal); fetch gender into eid,empname,sal; end loop; close gender; end; / Note: ecursor2.sql

declare eid emp.empid%type; empname emp.ename%type; sal emp.salary%type; gender emp.sex%type; bonus number(6,2); cursor e is select empid,ename,salary,sex from emp; begin open e; fetch e into eid,empname,sal,gender; while e%found loop if gender='M' then if sal < 3000 then bonus := sal*.2; else bonus := sal*.1; end if; else if sal < 3000 then bonus:= sal*.25; else bonus:=sal*.15; end if; dbms_output.put_line(eid || empname || sal||gender||bonus); fetch e into eid,empname,sal,gender; end loop; close e; end; / Note: EmpBonusCursor.SQL

Triggers A trigger is a program stored in the database and is called automatically when a triggering event occurs. Update events: –Insert, Delete, Update BEFORE Insert|Delete|Update ON tablename AFTER Insert|Delete|Update ON tablename Accessing new value and old value: –:NEW.fieldname –:OLD.fieldname FOR EACH ROW

Demo :New and :Old create or replace trigger changesal after update on emp for each row begin dbms_output.put_line(:old.ename || ' old salary is:' || :old.salary); dbms_output.put_line('new salary is: ' || :new.salary); end; / Note: EmpSaltrigger.sql

create or replace trigger adddetail before insert on orderdetail for each row declare stocks product.onhand%type; begin select onhand into stocks from hproduct where pid=:new.pid; if stocks < :new.qty then update product set onhand=0 where pid = :new.pid; dbms_output.put_line('not enough stock'); else update product set onhand=onhand - :new.qty where pid=:new.pid; end if; end; / Note: AddDetailTrigger.sql