E0018 null-comparison

Comparison with NULL using = or <> is never true.

What it reports

A comparison operator (=, <>, !=, <, <=, >, >=) with a NULL literal operand, and CASE x WHEN NULL. Any comparison with NULL is NULL, so the condition never holds and the WHEN branch never runs.

Example

SELECT name FROM users WHERE email = NULL;

warning[E0018]: Comparison with NULL using '=' is never true
  --> q.sql:1:30
    |
  1 | SELECT name FROM users WHERE email = NULL;
    |                              ^^^^^
    = help: Use IS NULL to test for NULL

Fixed:

SELECT name FROM users WHERE email IS NULL;

Notes

Assignments (UPDATE users SET email = NULL), IS [NOT] DISTINCT FROM NULL and MySQL's NULL-safe <=> are not comparisons in this sense and are not reported.

Configuring

# sqlsift.toml
[rules]
null-comparison = "error"   # or "off"

Or for a single line: -- sqlsift:disable E0018. The examples use the schema on the Rules page.