SQL CROSS JOIN
将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从联接表中返回行集合的笛卡尔积。
我们可以通过两种方式指定CROSS JOIN:
使用JOIN语法。
不使用WHERE子句的FROM子句中的表。
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-Departments
| Department_id |
Department_name |
| 1 |
IT |
| 2 |
HR |
| 3 |
Marketing |
SQL语句:
SELECT * FROM MatchScore CROSS JOIN Departments
执行此查询后，您将找到以下结果:
| 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 |
