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1.7 Loops

The LOOP construct allows you to execute a sequence of statements repeatedly. There are three kind of loops: simple (infinite), FOR, and WHILE.

You can use the EXIT statement to break out of LOOP and pass control to the statement following the END LOOP.

1.7.1 Simple Loop

LOOP
   executable_statement(s)
END LOOP;

The simple loop should contain an EXIT or EXIT WHEN unless you want it to execute infinitely. Use the simple loop when you want the body of the loop to execute at least once. For example:

LOOP
   FETCH company_cur INTO company_rec;
   EXIT WHEN company_cur%ROWCOUNT > 5 OR
      company_cur%NOTFOUND;
   process_company(company_cur);
END LOOP;

1.7.2 Numeric FOR Loop

FOR loop_index IN [REVERSE] lowest_number..highest_number
LOOP
   executable_statement(s)
END LOOP;

The PL/SQL runtime engine automatically declares the loop index a PLS_INTEGER variable; never declare a variable with that name yourself. The lowest_number and highest_number ranges can be variables, but are evaluated only once—on initial entry into the loop. The REVERSE keyword causes PL/SQL to start with the highest_number and decrement down to the lowest_number. For example, this code:

BEGIN
   FOR counter IN 1 .. 4
   LOOP
      DBMS_OUTPUT.PUT(counter);
   END LOOP;
   DBMS_OUTPUT.NEW_LINE;

   FOR counter IN REVERSE 1 .. 4
   LOOP
      DBMS_OUTPUT.PUT(counter);
   END LOOP;
   DBMS_OUTPUT.NEW_LINE;END;

yields the following output:

1234
4321

1.7.3 Cursor FOR Loop

FOR record_index IN [cursor_name | (SELECT statement)]
LOOP
   executable_statement(s)
END LOOP;

The PL/SQL runtime engine automatically declares the loop index a record of cursor_name%ROWTYPE; never declare a variable with that name yourself.

The cursor FOR loop automatically opens the cursor, fetches all rows identified by the cursor, and then closes the cursor. You can embed the SELECT statement directly in the cursor FOR loop. For example:

FOR emp_rec IN emp_cur
LOOP
   IF emp_rec.title = 'Oracle Programmer'
   THEN
      give_raise(emp_rec.emp_id,30)
   END IF;
END LOOP;

1.7.4 WHILE Loop

WHILE condition
LOOP
   executable_statement(s)
END LOOP;

Use the WHILE loop in cases where you may not want the loop body to execute even once:

WHILE NOT end_of_analysis
LOOP
   perform_analysis;
   get_next_record;
   IF analysis_cursor%NOTFOUND AND next_step IS NULL
   THEN
      end_of_analysis := TRUE;
   END IF;
END LOOP;

1.7.5 REPEAT UNTIL Loop Emulation

PL/SQL does not directly support a REPEAT UNTIL construct, but a modified simple loop can emulate one. The syntax for this emulated REPEAT UNTIL loop is:

LOOP
   executable_statement(s)
   EXIT WHEN Boolean_condition;
END LOOP;

Use the emulated REPEAT UNTIL loop when executing iterations indefinitely before conditionally terminating the loop.

1.7.6 EXIT Statement

EXIT [WHEN condition];

If you do not include a WHEN clause in the EXIT statement, it will terminate the loop unconditionally. Otherwise, the loop terminates only if the Boolean condition evaluates to TRUE. The EXIT statement is optional and can appear anywhere in the loop.

1.7.7 Loop Labels

Loops can be optionally labeled to improve readability and execution control, as we showed earlier in the discussion of the GOTO statement. The label must appear immediately in front of the statement that initiates the loop.

The following example demonstrates the use of loop labels to qualify variables within a loop and also to terminate nested and outer loops:

<<year_loop>>
FOR yearind IN 1 .. 20
LOOP
   <<month_loop>>
   LOOP
      ...
      IF year_loop.yearind > 10
      THEN
         EXIT year_loop;
      END IF;
   END LOOP month_loop;
END LOOP year_loop;
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