Boolean types v15

Overview

EDB Postgres Advanced Server provides the standard SQL type BOOLEAN. BOOLEAN can have one of only two states: TRUE or FALSE. A third state, UNKNOWN, is represented by the SQL NULL value.

Literal values representing the TRUE state include 'TRUE', 'true', 'y', '1', and 't'. Literal values representing FALSE include 'FALSE', 'false', 'n', '0' and 'f'. There's no literal value for UNKNOWN. Use NULL.

The follow is an example using the Boolean type:

CREATE TABLE test1 (a boolean, b text);
INSERT INTO test1 VALUES (TRUE, 'sic est');
INSERT INTO test1 VALUES (FALSE, 'non est');
SELECT * FROM test1;
 a |    b
---+---------
 t | sic est
 f | non est

SELECT * FROM test1 WHERE a;
 a |    b
---+---------
 t | sic est

The parser understands that TRUE and FALSE are of type Boolean, but this isn't so for NULL because that can have any type. So in some contexts you might have to cast NULL to BOOLEAN explicitly.

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