Question

我们有一个group和user permission表格如下：

Group (group_id,name)
01 | G1
02 | G2
03 | G3
04 | G4

UserPermission (userid,group_id,active)
User1 | 01 | 1
User1 | 02 | 1
User2 | 01 | 1
User2 | 02 | 1
User2 | 03 | 1
User2 | 04 | 1
..
UserN | xx | 1

每个用户都拥有群组的权限但UserPermission表中缺少某些用户的某些权限。

问题是为UserPermission表中的所有用户插入缺少的组权限条目。

所以我提出的查询是（原油）

 insert into UserPermission 
         select distinct userid, '03', 1 from UserPermission  
         where userid not in (
               select userid from UserPermission where group_id = '03'
         )

这是针对Group 03的用户缺少的插入权限与其他群体类似。

是否有更好的方法来编写上述查询。如何优化？

Answer 1

在我的解决方案中，我从表Group和UserPermission（唯一的用户ID ）获取了笛卡尔积。然后，使用UserPermission将两个表的产品连接回LEFT JOIN表，前提是它匹配两列：Group_ID和userID。任何不满足条件的记录在NULL的列上都会有UserPermission个值。这些值是UserPermission表中的缺失值。

这也将填充所有用户的所有遗漏权限。

INSERT INTO UserPermission(userID, group_ID, active)
SELECT  b.userID, a.Group_ID, 1
FROM    [Group] a
        CROSS JOIN (SELECT DISTINCT userID FROM UserPermission) b
        LEFT JOIN UserPermission c
            ON a.Group_ID = c.Group_ID AND
                b.userID = c.UserID
WHERE   c.Group_ID IS NULL

SQLFiddle Demo

但是如果你只想插入特定的Group_ID，那么你需要额外的条件。

INSERT INTO UserPermission(userID, group_ID, active)
SELECT  b.userID, a.Group_ID, 1
FROM    [Group] a
        CROSS JOIN (SELECT DISTINCT userID FROM UserPermission) b
        LEFT JOIN UserPermission c
            ON a.Group_ID = c.Group_ID AND
                b.userID = c.UserID
WHERE   c.Group_ID IS NULL AND
        a.Group_ID = 3
        -- or change it to IN clause
        -- if you have more Group_ID to include
        -- a.Group_ID IN (3,4)

SQLFiddle Demo

Answer 2

不存在通常比不存在更好。

insert into UserPermission
select disinct userid, '03', 1
from UserPermission
where not exists 
(select *
from UserPermission
where group_id = '03')

另一种方法是使用“in”而不是“not in”

insert into UserPermission
select disinct userid, '03', 1
from UserPermission
where user_id in 
(select user_id from UserPermission
except 
select user_id from UserPermission
where group_id = '03')

Answer 3

这是一种方式：

 with toinsert as (
    select userid, '03' as UserPermission
    from UserPermission up
    group by userId
    having sum9case when userPermission = '03' then 1 else 0 end) = 0
 )
 insert into UpserPermission
    select userid, UserPermission
    from toinsert;

我已将插入列表分解为CTE。您也可以像子查询一样执行此操作：

insert into UserPermission
    select userid, '03'
    from UserPermission
    group by userid
    having sum(case when userpermission = '03' then 1 else 0 end) = 0

Answer 4

另一种可能的解决方案是使用新的MERGE语句。根据我的经验，MERGE表现非常出色。

merge UserPermission target
using (
    -- Assuming u.userid and g.group_id are unique in their tables
    select u.userid, g.group_id
    from [User] u
    cross join [Group] g
) source on source.userid = target.userid and source.group_id = target.group_id
when not matched then
    insert (userid, group_id, active)
    values (source.userid, source.group_id, 1);

删除“NOT IN”子句并优化查询

4 个答案: