深入 CROSS JOIN

SQL 数据连接

Maham Faisal Khan

Senior Content Developer, DataCamp

CROSS JOIN 图示

CROSS JOIN 会生成两个表的所有组合。

一个图示显示两个表（table1 和 table2），箭头指向两表在 id 列上匹配的记录。与交叉连接无关的记录被灰显。右侧显示交叉连接后的结果集。

CROSS JOIN 语法

SELECT id1, id2
FROM table1
CROSS JOIN table2;

将总理与总统配对

SELECT prime_minister, president
FROM prime_ministers AS p1
CROSS JOIN presidents AS p2

WHERE p1.continent IN ('Asia')
    AND p2.continent IN ('South America');

|--------------------|-------------------------|
| prime_minister     | president               |
|--------------------|-------------------------|
| Shehbaz Sharif     | Luis Lacalle Pou        |
| Narendra Modi      | Luis Lacalle Pou        |
| Hassanal Bolkiah   | Luis Lacalle Pou        |
| Haitham bin Tarik  | Luis Lacalle Pou        |
| Shehbaz Sharif     | Gabriel Boric           |
| Narendra Modi      | Gabriel Boric           |
| Hassanal Bolkiah   | Gabriel Boric           |
| Haitham bin Tarik  | Gabriel Boric           |
|--------------------|-------------------------|

开始练习！

SQL 数据连接