myOra SQL提取表

Question

用户表

 userid   Name        

    1        Test1          

    2        Test2        

    3        Test3          

    4        Test4   

书桌

    userid   Destination       

    1        US

    2        UK

    1        MEXICO

    1        INDIA

    3        CANADA

    1        CHINA

    4        CANADA

    1        CHINA

根据上表，我应该使用什么方法在插入查询时显示此结果

这是我想要的结果

 bookCount   userid

    5        1          

    2        2        

    1        3          

    1        4   

Answer 1

试试这个：

SELECT COUNT(*) bookCount, userid
FROM Book
GROUP BY userid;

有关见解，请参阅MySQL GROUP BY。您不需要使用联接：

SELECT book.userid, COUNT(*) AS `count` 
FROM book INNER JOIN `user` ON book.userid=`user`.userid 
GROUP BY book.userid
HAVING COUNT(*)>1;