এটি বোঝার জন্য 'ছাত্রদের' টেবিল থেকে নিম্নরূপ ডেটা বিবেচনা করুন -
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)
এখন, ধরুন আমরা যদি জানতে চাই যে ছাত্রদের মধ্যে কতজন USA, UK, NZ, INDIA, RUSSIA, FRANCE ইত্যাদির, তাহলে আমরা CASE স্টেটমেন্টের মধ্যে কলাম 'country' ব্যবহার করতে পারি −
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)
