统计每一个商品每月的销量？？？

SELECT  M.B2B_SKU AS SKU,G.MATERIALNAME AS GOODNAME, SUM(CASE MONTH(O.SUBMITTIME) WHEN '1' THEN G.PURCHASQUANTITY ELSE 0 END) AS one,   SUM(CASE MONTH(O.SUBMITTIME) WHEN '2' THEN G.PURCHASQUANTITY ELS

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