What is While Loop?
WHILE loop statement works similar to the Basic loop statement except the EXIT condition is at the very beginning of the loop.
It works like an entry-check loop in which execution block will not even be executed once if the condition is not satisfied, as the exit condition is checking before execution part. It does not require keyword 'EXIT' explicitly to exit from the loop since it is validating the condition implicitly each time of the loop.
WHILE <EXIT condition> LOOP <execution block starts> . . . <execution_block_ends> END LOOP;Syntax Explanation:
- In the above syntax, keyword 'WHILE' marks beginning of the loop and 'END LOOP' marks the end of the loop.
- EXIT condition is evaluated each time before the execution part is starting executing.
- The execution block contains all the code that needs to be executed.
- The execution part can contain any execution statement.
Example 1: In this example, we are going to print number from 1 to 4 using WHILE loop statement. For that, we will execute the following code.
DECLARE a NUMBER :=1; BEGIN dbms_output.put_line('Program started'); WHILE (a <= 5) LOOP dbms_output.put_line(a); a:=a+1; END LOOP; dbms_output.put_line(‘Program completed' ); END: /
- Code line 2: Declaring the variable 'a' as 'NUMBER' data type and initializing it with value '1'.
- Code line 4: Printing the statement "Program started".
- Code line 5: Keyword 'WHILE' marks the beginning of the loop, and it also checks whether the value of 'a' is less than or equal to 5
- Code line 7: Prints the value of 'a'.
- Code line 8: Increments the value of 'a' by +1.
- Code line 9: Keyword 'END LOOP' marks the end of execution block.
- The code from line 7 and line 8 will continue to execute till 'a' reaches the value 6, as the condition will return TRUE, and the control will EXIT from the loop.
- Code line 10: Printing the statement "Program completed"
|EXIT Criteria||Exit when the check condition returns false|
|Usage||Good to use when the loop count is unknown, and exit is based on some other condition.|