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MySQL派生表聯(lián)表查詢實戰(zhàn)過程

更新時間：2022年03月19日 15:29:05 作者：用戶227807701855

派生表是查詢結(jié)果組成的虛擬表,派生表是在外部查詢的FROM子句中定義的,不需要手動創(chuàng)建,下面這篇文章主要給大家介紹了關(guān)于MySQL派生表聯(lián)表查詢的相關(guān)資料,需要的朋友可以參考下

前情提要：

公司運營的一個商城系統(tǒng)，忽然發(fā)現(xiàn)訂單提現(xiàn)功能有問題，有大量的商戶體現(xiàn)金額和訂單金額不一致。于是產(chǎn)生了需求，需要把提現(xiàn)表和供應(yīng)商表作為一個結(jié)果集，連接上訂單表中的訂單金額，通過計算訂單表的金額和體現(xiàn)表商戶提現(xiàn)的金額進(jìn)行比對，查看商戶是多提現(xiàn)了還是少提現(xiàn)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(xiàn)表為主表，查詢出來相關(guān)結(jié)果。MySQL語句如下

SELECT  count(ysw.supply_id) AS '提現(xiàn)次數(shù)',ysw.user_id AS '供應(yīng)商對應(yīng)的用戶ID', ysw.supply_id  AS '供應(yīng)商ID' ,SUM(ysw.money)  AS '供應(yīng)商提現(xiàn)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(yīng)商名稱',ys.money AS '供應(yīng)商余額',ys.freez_money AS '供應(yīng)商凍結(jié)金額（已提現(xiàn)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(jié)果如圖是正常的：

接下來，我在左鏈接上訂單表的數(shù)據(jù)，又添加一個了left join，金額相關(guān)數(shù)據(jù)發(fā)生了變化嚴(yán)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(xiàn)次數(shù)',ysw.user_id AS '供應(yīng)商對應(yīng)的用戶ID', ysw.supply_id  AS '供應(yīng)商ID' ,SUM(ysw.money)  AS '供應(yīng)商提現(xiàn)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(yīng)商名稱',ys.money AS '供應(yīng)商余額',ys.freez_money AS '供應(yīng)商凍結(jié)金額（已提現(xiàn)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(jié)果對比圖如下：

經(jīng)過實踐，我想直接通過左連接查詢到提現(xiàn)表金額和訂單表金額是行不通的。通過網(wǎng)上查資料，以及在技術(shù)群里請教，

優(yōu)化了思路：把提現(xiàn)的統(tǒng)計好,把訂單的統(tǒng)計好，最后兩個結(jié)果集再根據(jù)供應(yīng)商id做個鏈接

接下來就是，三步走了，第一步：把提現(xiàn)的統(tǒng)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(shù)據(jù)統(tǒng)計好。由于使用系統(tǒng)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.查詢yoshop_order所有進(jìn)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(yīng)商ID' , SUM(total_pay_price)  AS '供應(yīng)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(jìn)行把第一步和第二步的查詢結(jié)果當(dāng)作派生表，進(jìn)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(rèn)真看完，相信一定會有收貨。我在這里把我錯誤的過程也進(jìn)行了記錄第一次錯誤拼接：

SELECT * FROM  (
	SELECT  count(ysw.supply_id) AS '提現(xiàn)次數(shù)',ysw.user_id AS '供應(yīng)商對應(yīng)的用戶ID', ysw.supply_id  AS 'supply_id' ,SUM(ysw.money)  AS '供應(yīng)商提現(xiàn)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(yīng)商名稱',ys.money AS '供應(yīng)商余額',ys.freez_money AS '供應(yīng)商凍結(jié)金額（已提現(xiàn)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 ,這里是注釋記得刪除

SELECT * FROM   --  這里是錯誤的不應(yīng)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,并且在拼接的時候重復(fù)使用了select * from 。雖然是試錯了，但也是有收貨的，接下來進(jìn)行了第二次錯誤的拼接：

SELECT t1.提現(xiàn)次數(shù) ,t1.供應(yīng)商對應(yīng)的用戶ID ,t1.supply_id, t1.支付方式 ,t1.供應(yīng)商名稱,t1.供應(yīng)商余額, t1.供應(yīng)商凍結(jié)金額（已提現(xiàn)金額）, t2.total_pay_price FROM  (
SELECT  count(ysw.supply_id) AS '提現(xiàn)次數(shù)',ysw.user_id AS '供應(yīng)商對應(yīng)的用戶ID', ysw.supply_id  AS supply_id ,SUM(ysw.money)  AS '供應(yīng)商提現(xiàn)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(yīng)商名稱',ys.money AS '供應(yīng)商余額',ys.freez_money AS '供應(yīng)商凍結(jié)金額（已提現(xiàn)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(jù)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(yīng)該在開始查詢出來所有的字段，left join 后不能在使用select * 最后，回想了一遍自己所學(xué)的left join的語法，寫出了最后的正確的查詢結(jié)果

SELECT t1.supply_id '供應(yīng)商ID',t1.supply_name '供應(yīng)商名稱',t1.user_id '供應(yīng)商綁定的用戶ID',t1.withdrawtime '供應(yīng)商提現(xiàn)次數(shù)' ,t1.supplyallmoney '供應(yīng)商提現(xiàn)金額',t1.payway '供應(yīng)商提現(xiàn)方式',t1.supply_money '供應(yīng)商賬戶余額',t1.supply_free_money '供應(yīng)商凍結(jié)余額（已提現(xiàn)金額）',
t2.total_pay_price '供應(yīng)商訂單總金額',t2.order_id '供應(yīng)商訂單數(shù)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(jié)果截圖：

總結(jié)：

這次查詢的經(jīng)歷使我自己明顯的感覺到動手實戰(zhàn)才能提升自己的能力，加強(qiáng)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(jìn)行查詢，不要害怕查詢數(shù)據(jù)的復(fù)雜。第二：在派生表中盡量不要使用漢字作為字段名，只在最頂層select 查詢最終結(jié)果的時候在把字段名 as 為“漢字”，第三：熟悉記憶左連接和union 鏈接的查詢語法。

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