null-comparison (GN024)

Automatic fix is available.

What it does

Checks for comparison with NULL.

Why not?

Comparing NULL to NULL with = returns NULL, not true. Comparing a value to NULL returns neither true nor false, but NULL.

Do not write expression = NULL because NULL is not equal to NULL. (The null value represents an unknown value, and it is not known whether two unknown values are equal.)

When should you?

Never.

Use instead:

To check whether a value is or is not null, use the predicates:

• expression IS NULL
• expression IS NOT NULL