一个mysql查询问题

龙 宇 2016-7-27 微信营销 0 0

昨天写了个对于我来说很复杂的sql语句。 这里先放个图:
一个mysql查询问题

现在的需要的数据如图:从product表中拿到id,name两个字段,从buy_contract_Item和sale_contract_Item中拿到quantity,totalMoney这两个字段,再从buy_contract和sale_contract中拿到contract_date字段,同时以合同签定时间为查询条件将商品各类的数量和金额sum,最后返回获取结果。表与表的关联关系如图。

后来问了下同事,拿到了返回结果:

一开始就犯了个错误,虽然从 buy_contract_Item和sale_contract_Item获取的信息比较多,但却不能以他们为主表,这是昨天半天还没有结果的主要原因。因为所有后续的这些表都是以商品为主,为商品的买进和卖出服务的。所以这里以商品为主表做查询。

第一步:从product表中拿到Id,Name两个字段(其他的字段在后面扩充)

SELECT id,name FROM product

第二步:从buy_contract_item中拿到productId,SUM(quantity),SUM(totalMoney)这两个字

段并按组分类

--productId 为了后面与product表做关联条件的

SELECT productId,SUM(quantity),SUM(totalMoney)
FROM buy_contract_item
GROUP BY productId

第三步:从sale_contract_item中拿到SUM(quantity),SUM(totalMoney)这两个字段并按组

分类

SELECT
productId,SUM(quantity),SUM(totalMoney)
FROM sale_contract_item
GROUP BY productId

第四步: 对第二步的SELECT语句进行扩充,联结buy_contract:

获取SUM(quantity),SUM(totalMoney)和contract_date

SELECT productId,SUM(quantity),SUM(totalMoney),contract_date
FROM buy_contract_item a
JOIN buy_contract b ON a.contract_id = b.id
GROUP BY a.product_id;

第五步:添加where查询条件,另外再加上别名

SELECT productId,SUM(quantity) AS buyQuantity,SUM(totalMoney) AS buyTotalMoney,b.contract_date
FROM buy_contract_item a
JOIN buy_contract b ON a.contract_id = b.id
WHERE 1=1 and (b.contract_date >= '2015-03-13' and b.contract_date <= '2015-03-15')
GROUP BY a.product_id;

第六步:写出sale的情况和上面类似

SELECT productId,SUM(quantity) AS saleQuantity,SUM(totalMoney) AS saleTotalMoney,d.contract_date
FROM buy_contract_item c
JOIN buy_contract d ON c.contract_id = d.id
WHERE 1=1 and (d.contract_date >= '2015-03-13' and d.contract_date <= '2015-03-15')
GROUP BY c.product_id;

第一步、第五步、第六步左联结

SELECT t.id,t.name,
IFNULL(buyQuantity,0) AS buyQuantity,
IFNULL(buyTotalMoney,0) AS buyTotalMoney,
IFNULL(saleQuantity,0) AS saleQuantity,
IFNULL(saleTotalMoney,0) AS saleTotalMoney
FROM product t
LEFT JOIN
(
SELECT productId,SUM(quantity) AS buyQuantity,SUM(totalMoney) AS buyTotalMoney,b.contract_date
FROM buy_contract_item a
JOIN buy_contract b ON a.contract_id = b.id
WHERE 1=1 and (b.contract_date >= '2015-03-13' and b.contract_date <= '2015-03-15')
GROUP BY a.product_id;
) m ON t.id = m.productId
LEFT JOIN
(
SELECT productId,SUM(quantity) AS saleQuantity,SUM(totalMoney) AS saleTotalMoney,d.contract_date
FROM buy_contract_item c
JOIN buy_contract d ON c.contract_id = d.id
WHERE 1=1 and (d.contract_date >= '2015-03-13' and d.contract_date <= '2015-03-15')
GROUP BY c.product_id;
) n ON t.id = n.productId
ORDER BY buyQuantity DESC, saleQuantity DESC

写的中间可能还有错误,但大致思路是这样,复杂的sql语句,可以先写整体框架,然后在框架里不断的细化查询。

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