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;

Now You Try

Practice this concept

Product wants each feedback score classified as promoter, not promoter, or unknown when the NPS score is missing.

Available schema

product

Prefix tables with product.table_name.

iduser_idnps_scoreis_promoter

product.feedback

Column	Type
id	integer
user_id	integer
feature_id	integer
rating	integer
nps_score	integer
comment	text
created_at	timestamp with time zone
moderation_bucket	text

query.sql

Beginner business practice