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

登錄后復(fù)制

上述查詢(xún)將SUM()聚合函數(shù)與IF()函數(shù)結(jié)合使用，從“學(xué)生”表中獲取英語(yǔ)母語(yǔ)學(xué)生和非英語(yǔ)母語(yǔ)學(xué)生的輸出。

mysql> Select COUNT(IF(country = 'USA', 1, NULL))AS USA,
    -> COUNT(IF(country = 'UK', 1, NULL))AS UK,
    -> COUNT(IF(country = 'France', 1, NULL))AS France,
    -> COUNT(IF(country = 'Russia', 1, NULL))AS Russia,
    -> COUNT(IF(country = 'Australia', 1, NULL))AS Australia,
    -> COUNT(IF(country = 'INDIA', 1, NULL))AS INDIA,
    -> COUNT(IF(country = 'NZ', 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)

登錄后復(fù)制

上面的查詢(xún)將COUNT()聚合函數(shù)與IF()函數(shù)結(jié)合起來(lái)，以從“Students”表中獲取國(guó)家數(shù)量的輸出。

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