📅 最后修改于: 2020-11-11 09:37:36 🧑 作者: Mango
当第一张表的每一行与第二张表的每一行合并时，称为笛卡尔联接或交叉联接。一般而言，我们可以说SQL CROSS JOIN返回联接表中行集的笛卡尔积。
我们可以通过两种方式指定CROSS JOIN：
SQL Cross Join的语法
SELECT * FROM [TABLE1] CROSS JOIN [TABLE2]
OR
SELECT * FROM [ TABLE1] , [TABLE2]
让我们以两个表为例，
表1-MatchScore
| Player | Department_id | Goals |
|---|---|---|
| Franklin | 1 | 2 |
| Alan | 1 | 3 |
| Priyanka | 2 | 2 |
| Rajesh | 3 | 5 |
表2-部门
| Department_id | Department_name |
|---|---|
| 1 | IT |
| 2 | HR |
| 3 | Marketing |
SQL语句：
SELECT * FROM MatchScore CROSS JOIN Departments
执行完该查询后，您将发现以下结果：
| Player | Department_id | Goals | Depatment_id | Department_name |
|---|---|---|---|---|
| Franklin | 1 | 2 | 1 | IT |
| Alan | 1 | 3 | 1 | IT |
| Priyanka | 2 | 2 | 1 | IT |
| Rajesh | 3 | 5 | 1 | IT |
| Franklin | 1 | 2 | 2 | HR |
| Alan | 1 | 3 | 2 | HR |
| Priyanka | 2 | 2 | 2 | HR |
| Rajesh | 3 | 5 | 2 | HR |
| Franklin | 1 | 2 | 3 | Marketing |
| Alan | 1 | 3 | 3 | Marketing |
| Priyanka | 2 | 2 | 3 | Marketing |
| Rajesh | 3 | 5 | 3 | Marketing |