Question

我正在使用MySQL。我有以下查询：

SELECT DISTINCT c.car_id FROM cars AS c JOIN customer_cars bb ON bb.age=40;

当我运行上述查询时出现错误：

ERROR 1054 (42S22): Unknown column 'c.car_id' in 'field list'

我哪里错了？

（cars和customer_cars表都有car_id列）

Answer 1

你不能这样做：

SELECT DISTINCT car_id FROM customer_cars WHERE age = 40;

Answer 2

这对我没有任何错误

CREATE TEMPORARY TABLE cars (car_id INT NOT NULL);
CREATE TEMPORARY TABLE customer_cars (car_id INT NOT NULL, age INT NOT NULL);

SELECT DISTINCT c.car_id FROM cars AS c JOIN customer_cars bb ON bb.age=40;

这与连接条件也有效：

SELECT DISTINCT c.car_id 
FROM 
    cars AS c 
    JOIN 
    customer_cars bb USING (car_id)
WHERE 
    bb.age=40;

该错误不适用于该查询...

SQL查询中的未知列

2 个答案: