Question

是否可以使下面的代码工作。目前它只展示来自“纽约”的员工，而不是来自“芝加哥”的员工。？

SELECT employees.ename, zipcodes.city
FROM employees
LEFT JOIN zipcodes
ON employees.zip=zipcodes.zip
WHERE employees.zip =
(
SELECT zipcodes.zip
FROM zipcodes
WHERE zipcodes.city = 'New York' OR 'Chicago'
)
ORDER BY employees.eno;

提前致谢！

//勒

Answer 1

使用IN条件，如下所示：

SELECT employees.ename, zipcodes.city
FROM employees
LEFT JOIN zipcodes
ON employees.zip=zipcodes.zip
WHERE employees.zip IN
(
    SELECT zipcodes.zip
    FROM zipcodes
    WHERE zipcodes.city IN ('New York', 'Chicago')
)
ORDER BY employees.eno

另一种方法（可能更好）是使用JOIN条件本身而不是子查询，如下所示：

SELECT employees.ename, zipcodes.city
FROM employees
LEFT JOIN zipcodes
ON employees.zip=zipcodes.zip
AND zipcodes.city IN ('New York', 'Chicago')
ORDER BY employees.eno

MySQL子查询多个结果

1 个答案: