The NULL
statement is a no-op (no operation)—it passes control to the next statement without doing anything. In the body of an IF-THEN
clause, a loop, or a procedure, the NULL
statement serves as a placeholder.
The NULL
statement improves readability by making the meaning and action of conditional statements clear. It tells readers that the associated alternative was not overlooked, that you decided that no action is necessary.
Certain clauses in PL/SQL, such as in an IF
statement or an exception handler, must contain at least one executable statement. You can use the NULL
statement to make these constructs compile, while not taking any action.
You might not be able to branch to certain places with the GOTO
statement because the next statement is END
, END
IF
, and so on, which are not executable statements. In these cases, you can put a NULL
statement where you want to branch.
The NULL
statement and Boolean value NULL
are not related.