Question

我一直在搜索，似乎无法弄清楚如何获取以下内容，非常赞赏的任何帮助！

鉴于这些表格：

TABLE_1

+-----------+----------+-------+
| firstName | lastName |  zip  |
+-----------+----------+-------+
| John      | Doe      | 80210 |
| Barty     | Crouch   | 80598 |
| Mary      | Jane     | 80233 |
| John      | Doe      | 80210 |
+-----------+----------+-------+

TABLE_2

+-----------+----------+-------+
| firstName | lastName |  zip  |
+-----------+----------+-------+
| John      | Doe      | 80210 |
| Barty     | Crouch   | 80598 |
| Max       | Payne    | 80233 |
+-----------+----------+-------+

如何选择表之间的匹配记录，其中Table_1中的记录只有一个结果？

像这样的东西（作为查询应该做的例子写出的最终部分是我无法弄清楚的）

SELECT Table_1.firstName,
   Table_1.lastName,
   Table_1.zip,
   Table_2.firstName,
   Table_2.lastName,
    Table_2.zip
FROM Table_1, Table_2
WHERE Table_1.firstName = Table_2.firstName and Table_1.lastName = Table_2.lastName and Table_1.zip = Table_2.zip
and ONLY ONE RESULT First,Last,zip FROM TABLE_1

哪只会回归Barty Crouch 80598

Answer 1

加入一个派生表，该表是table_1中只有1个组计数的行的分组列表。：

SELECT T2.FirstName, T2.LastName, T2.Zip
FROM TABLE_2 AS T2
JOIN (
SELECT T1.FirstName, T1.LastName, T1.Zip
FROM TABLE_1 AS T1
GROUP BY T1.FirstName, T1.LastName, T1.Zip
HAVING COUNT(*) = 1) AS T1
  ON T1.FirstName = T2.FirstName
 AND T1.LastName = T2.LastName
 AND T1.Zip = T2.Zip

Answer 2

许多可能的变体之一：

SELECT Table_1.firstName,
   Table_1.lastName,
   Table_1.zip
FROM Table_1, Table_2
WHERE Table_1.firstName = Table_2.firstName and Table_1.lastName = Table_2.lastName and Table_1.zip = Table_2.zip
group by table_1.firstname, table_1.lastname, table_1.zip
having count(*) = 1

从两个表中选择WHERE只有1个来自table_1的唯一结果

2 个答案: