前情提要：
公司經營的一個商城系統，突然發現訂單提領功能有問題，有大量的商家體現金額和訂單金額不一致。於是產生了需求，需要把提現表和供應商表作為一個結果集，連接上訂單表中的訂單金額，透過計算訂單表的金額和體現表商戶提現的金額進行比對，查看商戶是多提現了還是少提現了。
下面記錄我的查詢過程。
查詢流程：
剛開始，第一步我以提現表為主表，查詢出相關結果。 MySQL語句如下
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 ;
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查詢結果如圖是正常的：
#接下來，我在左連結上訂單表的數據，又添加一個了left join，金額相關資料發生了變化嚴重不一致,而且查詢時間明顯延長，MySQL語句如下
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 ;
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查詢結果比較圖如下：
經過實踐，我想直接透過左連接查詢到提現表金額和訂單表金額是行不通的。透過網路上查資料，以及在技術群裡請教，
優化了思路： 把提現的統計好,把訂單的統計好， 最後兩個結果集再根據供應商id做個鏈接
接下來就是，三步走了， 第一步：把提現的統計好，上面第一次嘗試的第一步就是了， 第二步：把訂單表的數據統計好。由於使用系統的原因，我直接使用的訂單商品表計算的訂單總金額，這一步也是分三步走的，我直接上代碼：
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 ;
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接下來就是進行把第一步和第二步驟的查詢結果當作衍生表，進行左連接查詢。我在這一步耗費的時間和精力最多。如果你能認真看完，相信一定會有收貨。我在這裡把我錯誤的過程也進行了記錄第一次錯誤拼接：
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
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透過這一次試錯，明顯看出我把left join 和union all 的含義記錯了,並且在拼接的時候重複使用了select * from 。雖然是試錯了，但也是有收貨的，接下來進行了第二次錯誤的拼接：
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登入後複製
通過這兩次錯誤的嘗試，以及根據嘗試過程中MySQL給出的錯誤提示，知道自己是在左連接上使用錯誤了，應該在開始查詢出來所有的字段，left join 後不能在使用select * 最後，回想了一遍自己所學的left join的語法，寫出了最後的正確的查詢結果
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登入後複製
正確的結果截圖：
以上是MySQL派生表聯表查詢的範例分析的詳細內容。更多資訊請關注PHP中文網其他相關文章！
