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The main type of conditional control structure in PL/SQL is the IF statement, which enables conditional execution of statements. You can use the IF statement in three forms: IF-THEN, IF-THEN-ELSE, and IF-THEN-ELSEIF. Here s an example of a simple IF-THEN-ELSEIF statement: BEGIN . . . IF total_sales > 100000 THEN bonus := 5000; ELSEIF total_sales > 35000 THEN bonus := 500; ELSE bonus := 0; END IF; INSERT INTO new_payroll VALUES (emp_id, bonus . . .); END; /

PL/SQL loops provide a way to perform iterations of code for a specified number of times or until a certain condition is true or false. The following sections cover the basic types of looping constructs.

The simple loop construct encloses a set of SQL statements between the keywords LOOP and END LOOP. The EXIT statement ends the loop. You use the simple loop construct when you don t know how many times the loop should execute. The logic inside the LOOP and END LOOP statements decides when the loop is terminated. In the following example, the loop will be executed until a quality grade of 6 is reached: LOOP . . . if quality_grade > 5 . . . EXIT; end if; END LOOP;

Another simple loop type is the LOOP . . . EXIT . . . WHEN construct, which controls the duration of the loop with a WHEN statement. A condition is specified for the WHEN statement, and when this condition becomes true, the loop will terminate. Here s a simple example: DECLARE count_num NUMBER(6); BEGIN count_num := 1; LOOP dbms_output.put_line(' This is the current count count_num := count_num + 1; Exit when count_num > 100; END LOOP; END;

'|| count_num);

The WHILE loop specifies that a certain statement be executed while a certain condition is true. Note that the condition is evaluated outside the loop. Each time the statements within the LOOP and END LOOP statements are executed, the condition is evaluated. When the condition no longer holds true, the loop is exited. Here s an example of the WHILE loop: WHILE total <= 25000 LOOP . . . SELECT sal INTO salary FROM emp WHERE . . . total := total + salary; END LOOP;

The FOR loop is used when you want a statement to be executed a certain number of times. The FOR loop emulates the classic do loop that exists in most programming languages. Here s an example of the FOR loop:

BEGIN FOR count_num IN 1..100 LOOP dbms_output.put_line('The current count is : END LOOP; END;

'|| count_num);

Records in PL/SQL let you treat related data as a single unit. Records contain fields, with each field standing for a different item. You can use the %ROWTYPE attribute to declare a table s columns as a record, which uses the table as a cursor template, or you can create your own records. Here s a simple example of a record: DECLARE TYPE MeetingTyp IS RECORD ( date_held DATE, location VARCHAR2(20), purpose VARCHAR2(50)); To reference an individual field in a record, you use the dot notation, as shown here: MeetingTyp.location

An Oracle cursor is a handle to an area in memory that holds the result set of a SQL query, enabling you to individually process the rows in the result set. Oracle uses implicit cursors for all DML statements. Explicit cursors are created and used by application coders.

Implicit cursors are automatically used by Oracle every time you use a SELECT statement in PL/SQL. You can use implicit cursors in statements that return just one row. If your SQL statement returns more than one row, an error will result. In the following PL/SQL code block, the SELECT statement makes use of an implicit cursor: DECLARE emp_name varchar2(40); salary float; BEGIN SELECT emp_name, salary FROM employees WHERE employee_id=9999; dbms_output.put_line('employee_name : '||emp_name||' salary :'||salary); END; /