SELECT
    IF(a <=> NULL, 1, a),
    IF( a IS NULL, 1, a ),
    IF( a IS NOT NULL, a, 1 ),
    IF( ISNULL(a), 1, a ),
    IF( !ISNULL(a), a, 1 ),
    IF( !!ISNULL(a), 1, a ),
    IFNULL( a, 1 )
FROM
    (SELECT 1 as a) as tmp
GROUP BY
    a WITH ROLLUP

 
