1. PL/SQL

2. Introduction to PL/SQL PL/SQL is the procedure extension to Oracle SQL. It is used to access an Oracle database from various environments (e.g. Forms, Reports to create triggers, procedures, functions, etc.). PL/SQL provides high-level language features such as block structure, conditional statements, loop statements, variable types, structured data and customized error handling PL/SQL is integrated with the database server. It does not exist as a standalone language.

3. Basic Structure of PL/SQL The basic unit in PL/SQL is a block. All PL/SQL programs are made up of blocks, which can be nested within each other.

4. DECLARE /* Declarative section: variables, types, and local subprograms. */ BEGIN /* Executable section: procedural and SQL statements go here. */ /* This section of the block is required. */ EXCEPTION /* Exception handling section: error handling statements go here. */ END;

5. Only the executable section is required. The other sections are optional. The only SQL statements allowed in a PL/SQL program are SELECT, INSERT, UPDATE, DELETE and several other data manipulation statements plus some transaction control. Data definition statements like CREATE, DROP, or ALTER are not allowed.

6. The executable section also contains constructs such as assignments, branches, loops, procedure calls, and triggers. PL/SQL is not case sensitive. C style comments (/*... */) may be used, or for a one line comment precede it with (--). To execute a PL/SQL program, we must follow the program text itself by A line with a single dot ("."), and then A line with run;

7. Variables and Types Types in PL/SQL are the same as in SQL, in addition to the BOOLEAN type. Variables can be declared in the following ways: 1.Declare id NUMBER; name VARCHAR(20);

8. 2.Declare id emp.empno%TYPE; name emp.ename%TYPE; variable name table name column name

9. 3.Declare depttuple dept%ROWTYPE; depttuple will be a record that contains fields that represent the columns in table dept. depttuple(deptno,dname,location)

10. A variable can be intialized: Declare a NUMBER :=3; A variable can be constrained to not null: Declare a NUMBER NOT NULL:=3; Or a NUMBER NOT NULL DEFAULT 3;

11. Select statement Select statement has a different form SELECT column INTO variables FROM table WHERE condition; Select should return a single tuple, if several tuples are required, use a Cursor

12. Simple program Using the following table declaration: CREATE TABLE T1( e INTEGER, f INTEGER ); INSERT INTO T1 VALUES(1, 3); INSERT INTO T1 VALUES(2, 4);

13. DECLARE a NUMBER; b NUMBER; BEGIN SELECT e,f INTO a,b FROM T1 WHERE e>1; INSERT INTO T1 VALUES(b,a); END; ef 13 24 ef 13 24 42

14. Control Flow in PL/SQL IF-THEN-END-IF LOOP-EXIT WHEN-END LOOP FOR-END LOOP WHILE-END LOOP GOTO

15. IF-THEN-END-IF IF THEN ELSE END IF; IF THEN... ELSIF THEN......... ELSIF THEN... ELSE... END IF;

16. DECLARE a NUMBER; b NUMBER; BEGIN SELECT e,f INTO a,b FROM T1 WHERE e>1; IF b=1 THEN INSERT INTO T1 VALUES(b,a); ELSE INSERT INTO T1 VALUES(b+10,a+10); END IF; END;

17. LOOP-EXIT WHEN-END LOOP LOOP /* A list of statements. */ EXIT WHEN ; /*list of statements*/ END LOOP;

18. Insert each of the pairs (1, 1) through (100, 100) into T1 DECLARE i NUMBER := 1; BEGIN LOOP INSERT INTO T1 VALUES(i,i); i := i+1; EXIT WHEN i>100; END LOOP; END;

19. While - For WHILE LOOP END LOOP; FOR IN [REVERSE].. LOOP END LOOP; -- will be declared implicitly

20. Cursors A cursor is a variable that runs through the tuples of some relation. By fetching into the cursor each tuple of the relation, we can write a program to read and process the value of each such tuple. Ex: Delete every tuple whose first component is less than the second, and insert the reverse tuple into T1.

21. DECLARE /* Output variables to hold the result of the query: */ a T1.e%TYPE; b T1.f%TYPE; /* Cursor declaration: */ CURSOR T1Cursor IS SELECT e,f FROM T1 WHERE e < f FOR UPDATE;

22. BEGIN OPEN T1Cursor; LOOP /* Retrieve each row of the result of the above query into PL/SQL variables: */ FETCH T1Cursor INTO a, b; /* If there are no more rows to fetch, exit the loop: */ EXIT WHEN T1Cursor%NOTFOUND; /* Delete the current tuple: */ DELETE FROM T1 WHERE CURRENT OF T1Cursor; /* Insert the reverse tuple: */ INSERT INTO T1 VALUES(b, a); END LOOP; /* Free cursor used by the query. */ CLOSE T1Cursor; END;