MySQL派生表聯表查詢實戰過程

2022-03-19 19:00:58

前情提要：

公司運營的一個商城系統，忽然發現訂單提現功能有問題，有大量的商戶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，連線上訂單表中的訂單金額，通過計算訂單表的金額和體現表商戶提現的金額進行比對，檢視商戶是多提現了還是少提現了。

下面記錄我的查詢過程。

查詢過程：

剛開始，第一步我以提現表為主表，查詢出來相關結果。MySQL語句如下

SELECT  count(ysw.supply_id) AS '提現次數',ysw.user_id AS '供應商對應的使用者ID', ysw.supply_id  AS '供應商ID' ,SUM(ysw.money)  AS '供應商提現總金額',
case ysw.pay_type when 10 then '微信' when 20 then '支付寶' else '銀行卡' end as '支付方式' ,
ys.supply_name AS '供應商名稱',ys.money AS '供應商餘額',ys.freez_money AS '供應商凍結金額（已提現金額）'
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 ;

查詢結果如圖是正常的：

接下來，我在左連結上訂單表的資料，又新增一個了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 '提現次數',ysw.user_id AS '供應商對應的使用者ID', ysw.supply_id  AS '供應商ID' ,SUM(ysw.money)  AS '供應商提現總金額',
case ysw.pay_type when 10 then '微信' when 20 then '支付寶' else '銀行卡' end as '支付方式' ,
ys.supply_name AS '供應商名稱',ys.money AS '供應商餘額',ys.freez_money AS '供應商凍結金額（已提現金額）',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 ;

查詢結果對比圖如下：

經過實踐，我想直接通過左連線查詢到提現表金額和訂單表金額是行不通的。通過網上查資料，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做個連結

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：把訂單表的資料統計好。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，我直接上程式碼：

1.查詢yoshop_order所有進行中，已完成的 訂單id(order_id);
	SELECT order_id FROM yoshop_order WHERE order_status IN (10,30);
	
2.查詢沒有退款的訂單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.查詢訂單商品表中 所有的訂單金額

SELECT  supply_id  AS '供應商ID' , SUM(total_pay_price)  AS '供應商訂單總金額' 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 ;

接下來就是進行把第一步和第二步的查詢結果當作派生表，進行左連線查詢。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 '提現次數',ysw.user_id AS '供應商對應的使用者ID', ysw.supply_id  AS 'supply_id' ,SUM(ysw.money)  AS '供應商提現總金額',
	case ysw.pay_type when 10 then '微信' when 20 then '支付寶' else '銀行卡' end as '支付方式' ,
	ys.supply_name AS '供應商名稱',ys.money AS '供應商餘額',ys.freez_money AS '供應商凍結金額（已提現金額）'
	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 ,這裡是註釋記得刪除

SELECT * FROM   --  這裡是錯誤的不應該在查詢
		(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.提現次數 ,t1.供應商對應的使用者ID ,t1.supply_id, t1.支付方式 ,t1.供應商名稱,t1.供應商餘額, t1.供應商凍結金額（已提現金額）, t2.total_pay_price FROM  (
SELECT  count(ysw.supply_id) AS '提現次數',ysw.user_id AS '供應商對應的使用者ID', ysw.supply_id  AS supply_id ,SUM(ysw.money)  AS '供應商提現總金額',
case ysw.pay_type when 10 then '微信' when 20 then '支付寶' else '銀行卡' end as '支付方式' ,
	ys.supply_name AS '供應商名稱',ys.money AS '供應商餘額',ys.freez_money AS '供應商凍結金額（已提現金額）'
	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，知道自己是在左連線上使用錯誤了，應該在開始查詢出來所有的欄位，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 '供應商ID',t1.supply_name '供應商名稱',t1.user_id '供應商繫結的使用者ID',t1.withdrawtime '供應商提現次數' ,t1.supplyallmoney '供應商提現金額',t1.payway '供應商提現方式',t1.supply_money '供應商賬戶餘額',t1.supply_free_money '供應商凍結餘額（已提現金額）',
t2.total_pay_price '供應商訂單總金額',t2.order_id '供應商訂單數量'
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 '支付寶' else '銀行卡' 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

正確的結果截圖：

總結：

這次查詢的經歷使我自己明顯的感覺到動手實戰才能提升自己的能力，加強自己的記憶，在查詢的時候要注意以下幾點。第一：一步步的進行查詢，不要害怕查詢資料的複雜。第二：在派生表中儘量不要使用漢字作為欄位名，只在最頂層select 查詢最終結果的時候在把欄位名 as 為“漢字”，第三：熟悉記憶左連線和union 連結的查詢語法。

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MySQL派生表聯表查詢實戰過程

目錄

前情提要：

查詢過程：

總結：

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