Question

嗨，我在加入3张桌子时遇到了麻烦

table1(id1,name_1)

Table2(id2,top,name_2,fk_id1)

table3(id3,top,name_3,fk_id1)

因此我想要o：

tableResult(id1,name_1,top,name_2,name_3)

ps：top包含来自table2.top和table3.top

的数据

Answer 1

以下是我假设您的结果需要如下所示：

1. ID1, Name1, Top (from table 2), Name2, Name3
2. ID1, Name1, Top (from table 3), Name2, Name3

例如：

1. 514, Bill, 2, Sam, Jill
2. 514, Bill, 3, Sam, Jill
3. 515, Jack, 5, Bob, Tom
4. 515, Jack, 6, Bom, Tom

我认为您需要使用UNION ALL运算符。

SELECT A.ID_1, A.Name_1, B.Top, B.Name_2, C.Name_3
FROM Table1 AS A
LEFT OUTER JOIN Table2 AS B
ON A.Id_1 = B.Id_1
     LEFT OUTER JOIN Table3 AS C
     ON A.ID_1 = C.ID_1
UNION ALL
SELECT A.ID_1, A.Name_1, C.Top, B.Name_2, C.Name_3 --Notice that this grabs Top from Table 3
FROM Table1 AS A
LEFT OUTER JOIN Table2 AS B
ON A.Id_1 = B.Id_1
     LEFT OUTER JOIN Table3 AS C
     ON A.ID_1 = C.ID_1

我不确定您的规则，因此您可能需要使用与LEFT OUTER JOIN不同的联接。

Answer 2

如果您只想加入，下面的查询应该这样做。

SELECT *
FROM table1 a
JOIN table2 b ON b.fk_id1 = a.id1
JOIN table3 c ON c.fk_id1 = a.id1

如何将两列两个表插入到另一个表的一列中

2 个答案: