枚举SQL每条记录与@rownum：= @ ROWNUM + 1的rownum

Question

我在MySQL

SELECT 
@rownum:=@rownum+1 AS rownum, 
notifications_posts.from_user AS source, 
notifications_posts.on_post_id AS destination, 
notifications_posts.in_group_id, 
groups.group_name AS group_name, 
notifications_posts.on_post_id AS other_record_id, 
user_info.first_name, 
user_info.last_name, 
user_info.user_id, 
notifications_posts.date, 
posts.title AS 'title', 
user_rights.right AS 'right', 
'article' AS notification_type 
FROM notifications_posts 
INNER 
    JOIN user_info 
    ON notifications_posts.from_user = user_info.user_id 
INNER 
    JOIN posts 
    ON posts.id = notifications_posts.on_post_id 
INNER 
    JOIN groups 
    ON groups.group_id = notifications_posts.in_group_id 
INNER 
    JOIN user_rights 
    ON user_rights.group_id = notifications_posts.in_group_id AND user_rights.user_id = user_info.user_id 

此查询，我也得到

为什么我得到NULL在rownum ？

和所有第二，我通过ID需要组记录

GROUP BY rownum; 

谁能帮助我？

Answer 1

你与语句来初始化变量@rownum（SELECT ROWNUM：= 0）R

select @rownum:=@rownum+1 AS rownum,a.* 
    from 
    (SELECT 
     notifications_posts.from_user AS source, 
     notifications_posts.on_post_id AS destination, 
     notifications_posts.in_group_id, 
     groups.group_name AS group_name, 
     ........ 
     <remaining query> 
     )a,(SELECT @rownum:=0) r 

编辑：所以你的完整的查询应该是

​​

Answer 2

1. 套装在运行查询之前将rownum设置为0。
2. rownum的分组不会有什么区别 - rownum每行都会有所不同。

Answer 3

SELECT @rownum:=0; 
SELECT 
@rownum:=@rownum+1 AS rownum, 
notifications_posts.from_user AS source, 
notifications_posts.on_post_id AS destination, 
notifications_posts.in_group_id, 
groups.group_name AS group_name, 
notifications_posts.on_post_id AS other_record_id, 
user_info.first_name, 
user_info.last_name, 
user_info.user_id, 
notifications_posts.date, 
posts.title AS 'title', 
user_rights.right AS 'right', 
'article' AS notification_type 
FROM notifications_posts 
INNER 
    JOIN user_info 
    ON notifications_posts.from_user = user_info.user_id 
INNER 
    JOIN posts 
    ON posts.id = notifications_posts.on_post_id 
INNER 
    JOIN groups 
    ON groups.group_id = notifications_posts.in_group_id 
INNER 
    JOIN user_rights 
    ON user_rights.group_id = notifications_posts.in_group_id AND user_rights.user_id = user_info.user_id; 

Answer 4

我认为这是更优选地将只是为了结果（在MySQL），然后在你的应用程序中添加行号。如果你坚持：

警告：任何使用这种方式使用变量的查询，可能会在未来的MySQL版本中被破坏。

SELECT 
    @rownum := @rownum+1 AS rownum, 
    notifications_posts.from_user AS source, 
    notifications_posts.on_post_id AS destination, 
    notifications_posts.in_group_id, 
    groups.group_name AS group_name, 
    notifications_posts.on_post_id AS other_record_id, 
    user_info.first_name, 
    user_info.last_name, 
    user_info.user_id, 
    notifications_posts.date, 
    posts.title AS 'title', 
    user_rights.right AS 'right', 
    'article' AS notification_type 
FROM 
    (SELECT @rownum:=0) AS dummy     -- initial value 
CROSS 
    JOIN notifications_posts 
INNER 
    JOIN user_info 
    ON notifications_posts.from_user = user_info.user_id 
INNER 
    JOIN posts 
    ON posts.id = notifications_posts.on_post_id 
INNER 
    JOIN groups 
    ON groups.group_id = notifications_posts.in_group_id 
INNER 
    JOIN user_rights 
    ON user_rights.group_id = notifications_posts.in_group_id 
    AND user_rights.user_id = user_info.user_id 
ORDER BY           -- you need 
    whatever ;         -- ORDER BY clause