[英]MYSQL: SELECT DISTINCT only show rows which are unique
我只想查看“ Stadt”(=城市)列不等于“ Hauptstadt”(= Capital)的行。 我的桌子看起来像:
+----------------------+-------------------+--------------------------+---------------+
| 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(期望的输出):
+----------------------+-------------------+--------------------------+---------------+
| 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 |
+----------------------+-------------------+--------------------------+---------------+
我尝试了这个:
SELECT DISTINCT Name, Stadt, Land ,Hauptstadt
FROM Museum
GROUP BY 'Name', 'Stadt', 'Land', 'Hauptstadt'
ORDER BY Name;
输出:
+----------------------+----------+--------------------------+---------------+
| Name | Stadt | Land | Hauptstadt |
+----------------------+----------+--------------------------+---------------+
| Museum of Modern Art | New York | United States of America | Washington DC |
+----------------------+----------+--------------------------+---------------+
我的SELECT应该如何获得期望的输出?
谢谢你的帮助!
group by
的单引号使您感到困惑。 首先,仅对字符串和日期常量使用单引号。 其次,您几乎再也不需要group by
select distinct
group by
。 第三,您需要一个满足条件的where
子句。 所以试试这个:
SELECT DISTINCT Name, Stadt, Land ,Hauptstadt
FROM Museum
WHERE Stadt <> Hauptstadt
ORDER BY Name;
我们需要按名称分组,如果相等或不相等,则只比较两列
SELECT * FROM Museum WHERE Stadt != Hauptstadt GROUP BY Name;
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