MySQL SQL语句学习（查询某年每个月的销售额与采购额）

ELECT
    MONTH (orderTime) AS MONTH,
    SUM(
        CASE
        WHEN type = 0 THEN
            amount
        ELSE
            0
        END
    ) AS buy,
    SUM(
        CASE
        WHEN type = 1
        AND STATUS = 2 THEN
            amount
        ELSE
            0
        END
    ) AS sale