Select 警报类型和项目 ID 相同的一行以及相似的行数

Question

我正在尝试使我的项目的通知系统在用户方面尽可能简单。

"john brown and 4 others liked your photo"

我试过了：

Select a.id, a.item_id, a.type u.f_name, u.l_name, count(a)
From alerts
Join users on a.user_id = u.u_id
Where owner_id = {THE_USER_ID}

但它没有 "work"

用户table

u_id | f_name | l_name 
==========================
234    roy      wright    
654    pam      brown
564    kim      harris
334    tory     plummer
876    rick     forbes    
123    paul     nichol
980    mario    chang
454    todd     thompson
886    sam      richards
215    tash     gates
...    .....    ........

警报table

id   |   item_id   |   type    | user_id | owner_id
===================================================
1         21           like      234
2         21           comment   654
3         32           share     876
4         21           like      778
5         21           like      890
6         21           share     123
7         54           share     454
8         32           comment   655
9         60           comment   886
10        32           like      215
..        ..           ......    ...

我想要的结果

id | item_id | type   | u_id | f_name | l_name | amount_more 
============================================================
1    21       like     234    roy      wright    2
2    21       comment  654    pam      brown
3    32       comment  876    rick     forbes    
6    21       share    123    paul     nichol
7    54       share    454    todd     thompson
9    60       comment  886    sam      richards
10   32       like     215    tash     gates
..   ..       ....     ...    .....    ........

Answer 1

在查询中您没有正确使用别名 a 和 u，请使用：

Select 
a.id, 
a.item_id, 
a.type,
u.f_name, 
u.l_name, 
count(a.*)
From alerts a Join users u
on(a.user_id = u.u_id)
Where owner_id = {THE_USER_ID}
group by 1,2,3,4,5;

Answer 2

SELECT
    MIN(CASE WHEN RowNumber = 1 THEN id END) as Id
    ,item_id
    ,type
    ,MIN(CASE WHEN RowNumber = 1 THEN u_id END) as u_id
    ,MIN(CASE WHEN RowNumber = 1 THEN f_name END) as f_name
    ,MIN(CASE WHEN RowNumber = 1 THEN l_name END) as l_name
    ,COUNT(*) - 1 as amount_more
FROM
  (
    SELECT
        t.*
        ,(@rn:= if((@item = t.item_id) AND (@type = t.type),@rn + 1,
                   if((@item:=t.item_id) AND (@type:=t.type),1,1)
           )
        ) as RowNumber
    FROM
        (SELECT *
         FROM
            alerts a
            LEFT JOIN usersTbl u
            ON a.user_id = u.u_id
         WHERE
            a.owner_id = 201
         ORDER BY
             a.item_id
            ,a.type
            ,a.id) t
        CROSS JOIN (SELECT @rn:=0,@item:=0,@type:='') var
    ORDER BY
        item_id
        ,type
        ,id
   ) t2         
GROUP BY
    item_id
    ,type
ORDER BY
    id
;

因此您需要创建一个分区行号来标识您希望首先考虑的记录。然后使用条件聚合，您可以选择它作为您的用户。这有效在这里查看：http://rextester.com/VXZONO82847

Select 警报类型和项目 ID 相同的一行以及相似的行数

Select one row where alert type and item id are the same and also how many similar rows

mysql

sql

phoenix