LEFT JOIN改用INNER JOIN后面加条件,你怎么加的? 在ON后面加,and A.xiangce_id=2
SELECT A.xiangce_id, A.xiangce_title, count( * ) AS count FROM A,B where A.xiangce_id = B.xiangce_id GROUP BY B.xiangce_id
select * from A, (select xiangce_id, count(*) from B group by 1) t1 where A.xiangce_id=t1.xiangce_id
SELECT A.xiangce_id, A.xiangce_title, count( B.xiangpian_id) AS num FROM A LEFT JOIN B ON B.xiangce_id = A.xiangce_id GROUP BY A.xiangce_id, A.xiangce_title
SELECT A.xiangce_id, A.xiangce_title, count( * ) AS count FROM A,B where A.xiangce_id = B.xiangce_id and A.xiangce_id=2 GROUP BY B.xiangce_id
SELECT A.xiangce_id, A.xiangce_title, B.count( * ) AS num FROM A outer JOIN B ON B.xiangce_id = A.xiangce_id 具体参考,http://www.eduexam.cn/netschool/VF/5/21.htm
SELECT A.xiangce_id, A.xiangce_title, count( B.xiangpian_id) AS num FROM A LEFT JOIN B ON B.xiangce_id = A.xiangce_id GROUP BY A.xiangce_id, A.xiangce_title可以了,最终用的是这个,我之前写时没加GROUP BY就会没有结果,还有,如果要再加条件,要写在GROUP BY 前面,谢谢大家。
SELECT A.xiangce_id, A.xiangce_title, count( * ) AS num
FROM A
LEFT JOIN B ON B.xiangce_id = A.xiangce_id
GROUP BY A.xiangce_id
LIMIT 0 , 30试试
谢谢,好像有点问题,这样查询出来num的值是1,而实际数据库里是只有相册没有照片,还有,如果要查某个xiangce_id的值,后面加了条件xiangce_id=2,查询出来为空。
FROM A
LEFT JOIN B ON B.xiangce_id = A.xiangce_id
GROUP BY A.xiangce_id, A.xiangce_title
FROM A
outer JOIN B ON B.xiangce_id = A.xiangce_id 具体参考,http://www.eduexam.cn/netschool/VF/5/21.htm
FROM A
LEFT JOIN B ON B.xiangce_id = A.xiangce_id
GROUP BY A.xiangce_id, A.xiangce_title可以了,最终用的是这个,我之前写时没加GROUP BY就会没有结果,还有,如果要再加条件,要写在GROUP BY 前面,谢谢大家。