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Bool

Type bool is internally stored as UInt8. Possible values are true (1), false (0).

select true as col, toTypeName(col);
┌─col──┬─toTypeName(true)─┐
trueBool
└──────┴──────────────────┘

select true == 1 as col, toTypeName(col);
┌─col─┬─toTypeName(equals(true, 1))─┐
1 │ UInt8 │
└─────┴─────────────────────────────┘
CREATE TABLE test_bool
(
`A` Int64,
`B` Bool
)
ENGINE = Memory;

INSERT INTO test_bool VALUES (1, true),(2,0);

SELECT * FROM test_bool;
┌─A─┬─B─────┐
1true
2false
└───┴───────┘