Question

我在这里生气...

我想

SELECT `id` FROM `colors` 
  WHERE `colors.id=1` 
    AND `cars.user=1` 
    AND `colors.car=cars.id`

来自我的表格

users
id, name
1, Nicolas
2, John

cars
id, user, name
1, 1, Mercedes
2, 2, Ferrari

colors
id, car, name
1, 1, Black
2, 2, Red

这个数据库意味着，尼古拉斯有黑色梅赛德斯和约翰有红色法拉利例如，如果我使用带有WHERE colors.id=1 AND cars.user=2的SELECT语句，则需要返回一个空结果。

Answer 1

使用JOIN从所有表中获取结果。

SELECT u.name AS UserName, c.name AS CarName, col.name AS CarColor FROM users AS u
JOIN cars AS c ON (c.user = u.id)
JOIN colors AS col on (col.car = c.id)
WHERE u.id = 1;

从多个表的变量进行查询

1 个答案: