MySQL子查詢多個結果

Question

是否可以使下面的代碼正常工作。 目前，它僅顯示“紐約”的員工，而不顯示“芝加哥”的員工。

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;

提前致謝！

//勒

Answer 1

使用IN條件，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

另一種方法（可能是更好的方法）是使用JOIN條件本身而不是子查詢，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