SQL Boolean Data Type

Actually three-valued, not two — TRUE, FALSE, and NULL are all valid states.

What & Why

A BOOLEAN column holds TRUE or FALSE — but like every column type, it can also hold NULL, meaning "unknown" rather than either value. This is genuinely three-valued logic, not simple binary.

See How It Works

BOOLEAN RESULT — product.feedback

id	user_id	nps_score	is_promoter
1	101	9	TRUE
2	102	NULL	NULL
3	103	7	FALSE
4	104	NULL	NULL

The comparison `nps_score >= 8` produces a Boolean value: `TRUE` for 9, `FALSE` for 7, and `NULL` when the score itself is unknown.

EXAMPLE QUERY

SELECT id, user_id, nps_score,
  nps_score >= 8 AS is_promoter
FROM product.feedback;

Beginner business practice