Sequence control

Sequence control statements allow you to transfer control to a specified statement or skip it.

Compared with the IF and LOOP statements, the GOTO and NULL statements in sequence control statements are less important in PL/SQL programming. The GOTO statement is rarely used to jump to a specified statement. The NULL statement does not perform any action and is typically used to improve the readability of conditional statements.

GOTO statement

The GOTO statement allows you to unconditionally jump to another location in the code block and continue execution. You need to define a label in advance and then use GOTO to jump to the label. The label must be placed before a statement, not within a statement.

Here is an example:

obclient> DECLARE
    cnt NUMBER := 0;
BEGIN
    WHILE cnt < 3 LOOP
       DBMS_OUTPUT.PUT_LINE (cnt);
       cnt :=  cnt + 1;
       GOTO JUMP_OUT;
    END LOOP;
     cnt := 0;
     <<JUMP_OUT>>
    DBMS_OUTPUT.PUT_LINE (cnt);
END;
 /
Query OK, 0 rows affected

0
1

NULL statement

The NULL statement is an empty statement that does not perform any action and is typically used as a placeholder. For example, during code debugging, if the code is not yet fully written, you can use the NULL statement as a placeholder to avoid syntax errors.