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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_idWHERE ysw.create_time < 1647446400 AND ysw.apply_status IN (10,20,40) GROUP BY ysw.supply_idORDER 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_idLEFT 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_idORDER 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IDSELECT 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_idWHERE ysw.create_time < 1647446400 AND ysw.apply_status IN (10,20,40) GROUP BY ysw.supply_idORDER 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 t2ON 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_idWHERE ysw.create_time < 1647446400 AND ysw.apply_status IN (10,20,40) GROUP BY ysw.supply_idORDER 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 t2ON 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_moneyFROM yoshop_supply_withdraw AS ysw LEFT JOIN yoshop_supply AS ys ON ysw.supply_id = ys.supply_idWHERE ysw.create_time < 1647446400 AND ysw.apply_status IN (10,20,40) GROUP BY ysw.supply_idORDER 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 t2ON t1.supply_id = t2.supply_id正确的结果截图：
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