以下mysql查询用于获取2014年用户ID 31购买的每个项目的总销售额 .

SELECT

op.products_name,

ROUND(SUM( IF(MONTH(o.date_purchased) = 1, op.final_price * op.products_quantity,0)), 2) AS january,

ROUND(SUM( IF(MONTH(o.date_purchased) = 2, op.final_price * op.products_quantity,0)), 2) AS febraury,

ROUND(SUM( IF(MONTH(o.date_purchased) = 3, op.final_price * op.products_quantity,0)), 2) AS march,

ROUND(SUM( IF(MONTH(o.date_purchased) = 4, op.final_price * op.products_quantity,0)), 2) AS april,

ROUND(SUM( IF(MONTH(o.date_purchased) = 5, op.final_price * op.products_quantity,0)), 2) AS may,

ROUND(SUM( IF(MONTH(o.date_purchased) = 6, op.final_price * op.products_quantity,0)), 2) AS june,

ROUND(SUM( IF(MONTH(o.date_purchased) = 7, op.final_price * op.products_quantity,0)), 2) AS july,

ROUND(SUM( IF(MONTH(o.date_purchased) = 8, op.final_price * op.products_quantity,0)), 2) AS august,

ROUND(SUM( IF(MONTH(o.date_purchased) = 9, op.final_price * op.products_quantity,0)), 2) AS september,

ROUND(SUM( IF(MONTH(o.date_purchased) = 10, op.final_price * op.products_quantity,0)), 2) AS october,

ROUND(SUM( IF(MONTH(o.date_purchased) = 11, op.final_price * op.products_quantity,0)), 2) AS november,

ROUND(SUM( IF(MONTH(o.date_purchased) = 12, op.final_price * op.products_quantity,0)), 2) AS december

FROM orders_products op

LEFT JOIN orders o ON op.orders_id = o.orders_id

WHERE customers_id = 31

AND YEAR(o.date_purchased) = 2014

GROUP BY op.products_id

ORDER BY op.products_name

并且只有2个表可供使用 .

orders_products：orders_id，products_id，products_name ...

订单：orders_id，customers_id，date_purchased

我以为离开加入两个表会给我充分的未购买项目的NULL ...但它只给我购买的项目行 . 如何计算所有已购买/未购买商品的总销售额？

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