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GroupBy

Group By語法​

  • 用在分組統計
##### 語法 #####
SELECT columnnames FROM table WHERE condition GROUP BY columnname;

##### e.g. #####
SELECT aut_id, count(country) FROM book GROUP BY aut_id

mysql-groupby

Having語法​

  • GroupBy可以搭配Having將結果進一步篩選
##### 語法 #####
SELECT columnnames FROM table WHERE condition GROUP BY columnname HAVING codition;

##### e.g. #####
SELECT aut_id, count(country) FROM book GROUP BY aut_id HAVING count(country)>2