Question

评论表有store_idx，user_idx等...

我想创建一个查询语句，通过输入的user_id值获取用户已加入书签的商店信息。

我所做的查询句子是

select A.store_name
     , A.store_img
     , count(B.store_idx) as review_cnt 
  from board.store A 
  Left 
  Join board.review B 
    On A.store_idx is B.store_idx 
 where store_idx is (select A.store_idx from bookmark where user_id = ?)

然而，结果没有出现。

帮帮我......

Answer 1

请使用以下查询：

SELECT store_name
     , store_img
     , SUM(review_cnt) AS review_cnt
  FROM
     ( SELECT DISTINCT A.store_name
            , A.store_img
           , CASE WHEN B.store_idx IS NULL THEN 0 ELSE 1 END AS review_cnt
       FROM bookmark br
       JOIN board.store A 
            ON A.store_idx = br.store_idx
       LEFT 
           JOIN board.review B 
             ON A.store_idx = B.store_idx 
    WHERE br.user_id = ?
     )T

Answer 2

WHERE子句显然是过滤掉所有行。我们对此无能为力。但是您的查询也缺少GROUP BY，表别名可以改进，join条件不正确。

所以，试试这个版本：

select s.store_name, s.store_img, count(b.store_idx) as review_cnt 
from board.store s left join
     board.review r
     on s.store_idx = r.store_idx 
where b.store_idx in (select b.store_idx
                      from bookmark b
                      where b.user_id = ?
                     );

如何进行查询

2 个答案: