MYSQL：SELECT DISTINCT僅顯示唯一的行

Question

我只想查看“ Stadt”（=城市）列不等於“ Hauptstadt”（= Capital）的行。 我的桌子看起來像：

+----------------------+-------------------+--------------------------+---------------+
| Name                 | Stadt             | Land                     | Hauptstadt    |
+----------------------+-------------------+--------------------------+---------------+
| Kunstmuseum          | Bern              | Schweiz                  | Bern          |
| Musée Picasso        | Paris             | Frankreich               | Paris         |
| Museum Ludwig        | Köln              | Deutschland              | Berlin        |
| Museum of Modern Art | New York          | United States of America | Washington DC |
| Städel               | Frankfurt am Main | Deutschland              | Berlin        |
+----------------------+-------------------+--------------------------+---------------+

我只想看（期望的輸出）：

+----------------------+-------------------+--------------------------+---------------+
| Name                 | Stadt             | Land                     | Hauptstadt    |
+----------------------+-------------------+--------------------------+---------------+
| Museum Ludwig        | Köln              | Deutschland              | Berlin        |
| Museum of Modern Art | New York          | United States of America | Washington DC |
| Städel               | Frankfurt am Main | Deutschland              | Berlin        |
+----------------------+-------------------+--------------------------+---------------+

我嘗試了這個：

SELECT DISTINCT Name, Stadt, Land ,Hauptstadt 
FROM Museum 
GROUP BY 'Name', 'Stadt', 'Land', 'Hauptstadt' 
ORDER BY Name;

輸出：

+----------------------+----------+--------------------------+---------------+
| Name                 | Stadt    | Land                     | Hauptstadt    |
+----------------------+----------+--------------------------+---------------+
| Museum of Modern Art | New York | United States of America | Washington DC |
+----------------------+----------+--------------------------+---------------+

我的SELECT應該如何獲得期望的輸出？

謝謝你的幫助！

Answer 1

group by的單引號使您感到困惑。 首先，僅對字符串和日期常量使用單引號。 其次，您幾乎再也不需要group by select distinct group by 。 第三，您需要一個滿足條件的where子句。 所以試試這個：

SELECT DISTINCT Name, Stadt, Land ,Hauptstadt 
FROM Museum 
WHERE Stadt <> Hauptstadt
ORDER BY Name;

Answer 2

我們需要按名稱分組，如果相等或不相等，則只比較兩列

SELECT * FROM Museum WHERE Stadt != Hauptstadt GROUP BY Name;