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9.5.6 Doing Nothing At All

Sometimes a placeholder statement that does nothing is useful. For example, it can indicate that one arm of an if/then/else chain is deliberately empty. For this purpose, use the NULL statement:

NULL;

For example, the following two fragments of code are equivalent:

BEGIN
    y := x / 0;
EXCEPTION
    WHEN division_by_zero THEN
        NULL;  -- ignore the error
END;

BEGIN
    y := x / 0;
EXCEPTION
    WHEN division_by_zero THEN  -- ignore the error
END;

Which is preferable is a matter of taste.

Note: In Oracle's PL/SQL, empty statement lists are not allowed, and so NULL statements are required for situations such as this. PL/pgSQL allows you to just write nothing, instead.