本文小编为大家详细介绍“MySQL派生表联表查询的方法是什么”,内容详细,步骤清晰,细节处理妥当,希望这篇“MySQL派生表联表查询的方法是什么”文章能帮助大家解决疑惑,下面跟着小编的思路慢慢深入,一起来学习新知识吧。
前情提要:
公司运营的一个商城系统,忽然发现订单提现功能有问题,有大量的商户体现金额和订单金额不一致。于是产生了需求,需要把提现表和供应商表作为一个结果集,连接上订单表中的订单金额,通过计算订单表的金额和体现表商户提现的金额进行比对,查看商户是多提现了还是少提现了。
下面记录我的查询过程。
查询过程:
刚开始,第一步我以提现表为主表,查询出来相关结果。MySQL语句如下
SELECT count(ysw.supply_id) AS '提现次数',ysw.user_id AS '供应商对应的用户ID', ysw.supply_id AS '供应商ID' ,SUM(ysw.money) AS '供应商提现总金额', case ysw.pay_type when 10 then '微信' when 20 then '支付宝' else '银行卡' end as '支付方式' , ys.supply_name AS '供应商名称',ys.money AS '供应商余额',ys.freez_money AS '供应商冻结金额(已提现金额)' FROM yoshop_supply_withdraw AS ysw LEFT JOIN yoshop_supply AS ys ON ysw.supply_id = ys.supply_id WHERE ysw.create_time < 1647446400 AND ysw.apply_status IN (10,20,40) GROUP BY ysw.supply_id ORDER BY SUM(ysw.money) DESC ;
查询结果如图是正常的:
接下来,我在左链接上订单表的数据,又添加一个了left join,金额相关数据发生了变化严重不一致,而且查询时间明显延长,MySQL语句如下
SELECT count(ysw.supply_id) AS '提现次数',ysw.user_id AS '供应商对应的用户ID', ysw.supply_id AS '供应商ID' ,SUM(ysw.money) AS '供应商提现总金额', case ysw.pay_type when 10 then '微信' when 20 then '支付宝' else '银行卡' end as '支付方式' , ys.supply_name AS '供应商名称',ys.money AS '供应商余额',ys.freez_money AS '供应商冻结金额(已提现金额)',SUM(yo.pay_price) FROM yoshop_supply_withdraw AS ysw LEFT JOIN yoshop_supply AS ys ON ysw.supply_id = ys.supply_id LEFT JOIN yoshop_order AS yo ON yo.supply_ids =ysw.supply_id WHERE ysw.create_time < 1647446400 AND ysw.apply_status IN (10,20,40) GROUP BY ysw.supply_id ORDER BY SUM(ysw.money) DESC ;
查询结果对比图如下:
经过实践,我想直接通过左连接查询到提现表金额和订单表金额是行不通的。通过网上查资料,以及在技术群里请教,
优化了思路: 把提现的统计好,把订单的统计好, 最后两个结果集再根据供应商id做个链接
接下来就是,三步走了, 第一步:把提现的统计好,上面第一次尝试的第一步就是了, 第二步:把订单表的数据统计好。由于使用系统的原因,我直接使用的订单商品表计算的订单总金额,这一步也是分三步走的,我直接上代码:
1.查询yoshop_order所有进行中,已完成的 订单id(order_id); SELECT order_id FROM yoshop_order WHERE order_status IN (10,30); 2.查询没有退款的订单ID SELECT order_id FROM yoshop_order WHERE order_status IN (10,30) AND order_id NOT IN ( SELECT order_id FROM yoshop_order_refund); 3.查询订单商品表中 所有的订单金额 SELECT supply_id AS '供应商ID' , SUM(total_pay_price) AS '供应商订单总金额' FROM yoshop_order_goods WHERE create_time < 1647446400 AND order_pay_status = 0 AND order_id IN(SELECT order_id FROM yoshop_order WHERE order_status IN (10,30) AND order_id NOT IN ( SELECT order_id FROM yoshop_order_refund) ) GROUP BY supply_id ORDER BY SUM(total_pay_price) DESC ;
接下来就是进行把第一步和第二步的查询结果当作派生表,进行左连接查询。我在这一步耗费的时间和精力最多。如果你能认真看完,相信一定会有收货。我在这里把我错误的过程也进行了记录 第一次错误拼接:
SELECT * FROM ( SELECT count(ysw.supply_id) AS '提现次数',ysw.user_id AS '供应商对应的用户ID', ysw.supply_id AS 'supply_id' ,SUM(ysw.money) AS '供应商提现总金额', case ysw.pay_type when 10 then '微信' when 20 then '支付宝' else '银行卡' end as '支付方式' , ys.supply_name AS '供应商名称',ys.money AS '供应商余额',ys.freez_money AS '供应商冻结金额(已提现金额)' FROM yoshop_supply_withdraw AS ysw LEFT JOIN yoshop_supply AS ys ON ysw.supply_id = ys.supply_id WHERE ysw.create_time < 1647446400 AND ysw.apply_status IN (10,20,40) GROUP BY ysw.supply_id ORDER BY SUM(ysw.money) DESC ) AS t1 union all // left join ,这里是注释记得删除 SELECT * FROM -- 这里是错误的不应该在查询 (SELECT supply_id AS 'supply_id' , SUM(total_pay_price) AS total_pay_price FROM yoshop_order_goods WHERE create_time < 1647446400 AND order_pay_status = 0 AND order_id IN( SELECT order_id FROM yoshop_order WHERE order_status IN (10,30) AND order_id NOT IN ( SELECT order_id FROM yoshop_order_refund) ) GROUP BY supply_id ORDER BY SUM(total_pay_price) DESC ) AS t2 ON t1.suppply_id = t2.suppply_id
通过这一次试错,明显看出我把left join 和 union all 的含义记错了,并且在拼接的时候重复使用了select * from 。虽然是试错了,但也是有收货的,接下来进行了第二次错误的拼接:
SELECT t1.提现次数 ,t1.供应商对应的用户ID ,t1.supply_id, t1.支付方式 ,t1.供应商名称,t1.供应商余额, t1.供应商冻结金额(已提现金额), t2.total_pay_price FROM ( SELECT count(ysw.supply_id) AS '提现次数',ysw.user_id AS '供应商对应的用户ID', ysw.supply_id AS supply_id ,SUM(ysw.money) AS '供应商提现总金额', case ysw.pay_type when 10 then '微信' when 20 then '支付宝' else '银行卡' end as '支付方式' , ys.supply_name AS '供应商名称',ys.money AS '供应商余额',ys.freez_money AS '供应商冻结金额(已提现金额)' FROM yoshop_supply_withdraw AS ysw LEFT JOIN yoshop_supply AS ys ON ysw.supply_id = ys.supply_id WHERE ysw.create_time < 1647446400 AND ysw.apply_status IN (10,20,40) GROUP BY ysw.supply_id ORDER BY SUM(ysw.money) DESC ) AS t1 LEFT JOIN (SELECT supply_id AS supply_id , SUM(total_pay_price) AS total_pay_price FROM yoshop_order_goods WHERE create_time < 1647446400 AND order_pay_status = 0 AND order_id IN( SELECT order_id FROM yoshop_order WHERE order_status IN (10,30) AND order_id NOT IN ( SELECT order_id FROM yoshop_order_refund) ) GROUP BY supply_id ORDER BY SUM(total_pay_price) DESC ) AS t2 ON t1.suppply_id = t2.suppply_id
通过这两次错误的尝试,以及根据尝试过程中MySQL给出的错误提示,知道自己是在左连接上使用错误了,应该在开始查询出来所有的字段,left join 后不能在使用select * 最后,回想了一遍自己所学的left join的语法,写出了最后的正确的查询结果
SELECT t1.supply_id '供应商ID',t1.supply_name '供应商名称',t1.user_id '供应商绑定的用户ID',t1.withdrawtime '供应商提现次数' ,t1.supplyallmoney '供应商提现金额',t1.payway '供应商提现方式',t1.supply_money '供应商账户余额',t1.supply_free_money '供应商冻结余额(已提现金额)', t2.total_pay_price '供应商订单总金额',t2.order_id '供应商订单数量' FROM ( SELECT count(ysw.supply_id) AS withdrawtime, ysw.user_id AS user_id, ysw.supply_id AS supply_id , SUM(ysw.money) AS supplyallmoney, ysw.alipay_name AS alipay_name ,ysw.alipay_account AS alipay_account, ysw.audit_time as audit_time , ysw.bank_account AS bank_account, ysw.bank_card AS bank_card, ysw.bank_name AS bank_name, case ysw.pay_type when 10 then '微信' when 20 then '支付宝' else '银行卡' end as payway , ys.supply_name AS supply_name, ys.money AS supply_money, ys.freez_money AS supply_free_money FROM yoshop_supply_withdraw AS ysw LEFT JOIN yoshop_supply AS ys ON ysw.supply_id = ys.supply_id WHERE ysw.create_time < 1647446400 AND ysw.apply_status IN (10,20,40) GROUP BY ysw.supply_id ORDER BY SUM(ysw.money) DESC ) AS t1 LEFT JOIN (SELECT supply_id AS 'supply_id' , COUNT(order_id) AS order_id, SUM(total_pay_price) AS total_pay_price FROM yoshop_order_goods WHERE create_time < 1647446400 AND order_pay_status = 0 AND order_id IN( SELECT order_id FROM yoshop_order WHERE order_status IN (10,30) AND order_id NOT IN ( SELECT order_id FROM yoshop_order_refund) ) GROUP BY supply_id ORDER BY SUM(total_pay_price) DESC ) AS t2 ON t1.supply_id = t2.supply_id
正确的结果截图: