이를 이해하기 위해 'Students' 표의 데이터를 다음과 같이 고려하십시오. −
mysql> Select * from Students; +----+-----------+-----------+----------+----------------+ | id | Name | Country | Language | Course | +----+-----------+-----------+----------+----------------+ | 1 | Francis | UK | English | Literature | | 2 | Rick | USA | English | History | | 3 | Correy | USA | English | Computers | | 4 | Shane | France | French | Computers | | 5 | Validimir | Russia | Russian | Computers | | 6 | Steve | Australia | English | Geoinformatics | | 7 | Rahul | India | Hindi | Yoga | | 8 | Harshit | India | Hindi | Computers | | 9 | Harry | NZ | English | Electronics | +----+-----------+-----------+----------+----------------+ 9 rows in set (0.00 sec)
이제 USA, UK, NZ, INDIA, RUSSIA, FRANCE 등에 속한 학생 수를 알고 싶다면 CASE 문 내에서 'country' 열을 다음과 같이 사용할 수 있습니다. -
mysql> Select SUM(CASE WHEN country = 'USA' THEN 1 ELSE 0 END) AS USA, -> SUM(CASE WHEN country = 'UK' THEN 1 ELSE 0 END) AS UK, -> SUM(CASE WHEN country = 'INDIA' THEN 1 ELSE 0 END) AS INDIA, -> SUM(CASE WHEN country = 'Russia' THEN 1 ELSE 0 END) AS Russia, -> SUM(CASE WHEN country = 'France' THEN 1 ELSE 0 END) AS France, -> SUM(CASE WHEN country = 'NZ' THEN 1 ELSE 0 END) AS NZ, -> SUM(CASE WHEN country = 'Australia' THEN 1 ELSE 0 END) AS Australia -> From Students; +------+------+-------+--------+--------+------+-----------+ | USA | UK | INDIA | Russia | France | NZ | Australia | +------+------+-------+--------+--------+------+-----------+ | 2 | 1 | 2 | 1 | 1 | 1 | 1 | +------+------+-------+--------+--------+------+-----------+ 1 row in set (0.07 sec)