查询具有相同字段项的两个不同表答案

【问题标题】：Query Two Different Table that have same field item查询具有相同字段项的两个不同表
【发布时间】：2013-12-23 20:04:48
【问题描述】：

我有两张桌子

表_A

ID PostId 项目股票价格 1 1 30 10 2 1 乙 40 20 3 2 50 5 4 3 一个 50 25

表_B

ID PostId Item_ID 售价 1 1 1 2 20 2 1 2 2 40 3 1 1 1 10 4 2 3 3 15 5 2 3 1 5

我想从上面两个表中查询具有相同的“PostID”和 COUNT 并通过“PostID”对某些字段组求和，预期的输出会是这样的

输出

ID PostId Total Item Total Stock Total Buyer(s) Total Sold Total Price 1 1 2 70 3 5 70

我尝试加入它，但结果仍然无法计算

SELECT Table_A.PostId AS PostId, COUNT(Table_A.Item) AS Total_Item, SUM(Table_A.stock) AS Total_Stock, COUNT(Table_B.Item_ID) AS total_buyer, SUM( Table_B.Sold ) AS TotalSold, SUM( Table_B.Price ) AS Total_Price
FROM Table_A
LEFT JOIN Table_B
ON Table_A.PostId = Table_B.PostId
WHERE Table_A.PostId = '1'
GROUP BY Table_A.PostId
LIMIT 0 , 30

对这个查询问题有什么建议吗？谢谢

【问题讨论】：

标签： sql join

【解决方案1】：

SELECT Table_B.PostId AS PostId, 
       MIN(Table_A.Total_Item) AS Total_Item, 
       MIN(Table_A.Total_Stock) AS Total_Stock, 
       COUNT(Table_B.Item_ID) AS total_buyer, 
       SUM( Table_B.Sold ) AS TotalSold, 
       SUM( Table_B.Price ) AS Total_Price
FROM Table_B
LEFT JOIN 
(
SELECT PostId,
       COUNT(Item) AS Total_Item,
       SUM(stock) AS Total_Stock
FROM
Table_A
GROUP BY PostId
) Table_A
ON Table_B.PostId=Table_A.PostId
WHERE Table_B.PostId = '1'
GROUP BY Table_B.PostId
LIMIT 0 , 30

【讨论】：