MSSQL – UPDATE CASE WHEN
UPDATE tbl_persons SET gender_description = CASE WHEN gender = '1' THEN 'male' WHEN gender = '2' THEN 'female' ELSE 'unknown' END
UPDATE tbl_persons SET gender_description = CASE WHEN gender = '1' THEN 'male' WHEN gender = '2' THEN 'female' ELSE 'unknown' END