SUM(
CASE WHEN rmstrancde IN ('50','51','52','53')
THEN (0 - ABS(DISTINCT rmstranamt))
WHEN rmstrancde IN ('55','56','57','58')
THEN ABS(DISTINCT rmstranamt)
ELSE
DISTINCT rmstranamt
END
) As rmstranamt
ERROR: 'ABS' is not a recognized function name.