SELECT
mergebuys.pTime,
(mergebuys.M1 - aggregates.AVGM1) / aggregates.STDM1 AS z1,
(mergebuys.M2 - aggregates.AVGM2) / aggregates.STDM2 AS z2,
(mergebuys.M3 - aggregates.AVGM3) / aggregates.STDM3 AS z3,
(mergebuys.M4 - aggregates.AVGM4) / aggregates.STDM4 AS z4
FROM
mergebuys
CROSS JOIN (
SELECT
AVG(M1) AS AVGM1,
STD(M1) AS STDM1,
AVG(M2) AS AVGM2,
STD(M2) AS STDM2,
AVG(M3) AS AVGM3,
STD(M3) AS STDM3,
AVG(M4) AS AVGM4,
STD(M4) AS STDM4
FROM
mergebuys
) AS aggregates