MySQL聚合函數如何與MySQL IF()函式結合？-mysql教程-PHP中文網

MySQL聚合函數如何與MySQL IF()函式結合？

WBOY

發布： 2023-08-27 13:37:13

轉載

777 人瀏覽過

MySQL聚合函数如何与MySQL IF()函数结合？

Combining MySQL aggregate functions with MySQL IF() function can be very helpful to get the specific output we want. Consider the following queries which combine SUM() and COUNT() aggregate functions with IF() function.

Example

mysql> Select SUM(IF(Language = &#39;English&#39;, 1, 0)) As English, SUM(IF(Language <> &#39;English&#39;,1,0)) AS "Non-English" from Students;
+---------+-------------+
| English | Non-English |
+---------+-------------+
| 5       | 4           |
+---------+-------------+
1 row in set (0.00 sec)

登入後複製

上述查詢將SUM()聚合函數與IF()函數結合使用，從「學生」表中取得英文母語學生與非英語母語學生的輸出。

mysql> Select COUNT(IF(country = &#39;USA&#39;, 1, NULL))AS USA,
    -> COUNT(IF(country = &#39;UK&#39;, 1, NULL))AS UK,
    -> COUNT(IF(country = &#39;France&#39;, 1, NULL))AS France,
    -> COUNT(IF(country = &#39;Russia&#39;, 1, NULL))AS Russia,
    -> COUNT(IF(country = &#39;Australia&#39;, 1, NULL))AS Australia,
    -> COUNT(IF(country = &#39;INDIA&#39;, 1, NULL))AS INDIA,
    -> COUNT(IF(country = &#39;NZ&#39;, 1, NULL))AS NZ FROM Students;
+-----+----+--------+--------+-----------+-------+----+
| USA | UK | France | Russia | Australia | INDIA | NZ |
+-----+----+--------+--------+-----------+-------+----+
| 2   | 1  | 1      | 1      | 1         | 2     | 1  |
+-----+----+--------+--------+-----------+-------+----+
1 row in set (0.07 sec)

登入後複製

上面的查詢將COUNT()聚合函數與IF()函數結合起來，以從「Students」表中取得國家數量的輸出。

以上是MySQL聚合函數如何與MySQL IF()函式結合？的詳細內容。更多資訊請關注PHP中文網其他相關文章！