why do we declare a bool as bit in mysql code example

Example 1: boolean mysql

-- MySQL doesn't have a boolean. Instead, use TINYINT. BOOL and BOOLEAN
-- are aliases to TINYINT. 0 is true, while 1 is false for TINYINT.
-- You can also use TRUE, FALSE, true, false, True, or false as
-- aliases for 0 and 1 respectively.

CREATE TABLE IF NOT EXISTS boolTest (
  thisFieldIsTrue TINYINT DEFAULT 0 -- True by default
  thisFieldIsFalse TINYINT DEFAULT 1 -- False by default
  thisIsAlsoTru BOOL DEFAULT True -- True by default, see above for alternates to True and Bool
 )

Example 2: boolean mysql

SELECT true, false, TRUE, FALSE, True, False;
-- 1 0 1 0 1 0