Question

我有3个表：Permissions，Role和RolePermissions。我想有一种方法可以基于RolePermissions表关系在Permissions表中选择缺少新行的Roles，以便在添加新权限后插入这些值。

我没有运气找到如何做到的，这就是为什么我在这里问。

表结构

Permissions | Roles | RolePermissions
------------------------------------------
Id          | Id    | Id
Name        | Name  | RoleId
            |       | PermissionId

sql的想法，但我知道这是不正确的：

-- Looking to be able to do something like
INSERT INTO RolePermissions (RoleId, PermissionId)
SELECT missingpermissions.PermissionId, missingpermissions.RoleId
FROM Permissions as p
INNER JOIN(
Select r.Id as RoleId,  p.Id as PermissionId
    FROM Role as r
    LEFT JOIN RolePermissions as rp
        ON r.Id = rp.RoleId
    WHERE rp.PermissionId = p.Id
) as missingpermissions 
ON p.id = missingpermissions.permissionid

已编辑为格式

Answer 1

您需要获得新的权限并交叉加入所有角色（以获取角色和新权限的所有组合）。

INSERT INTO RolePermissions(RoleId, PermissionId)
    SELECT r.ID AS RoleId,p.ID AS PermissionId
    FROM Role r
    CROSS JOIN (
       --get all permissions currently not assigned to a role (presumably "new")
       select p.*
       from Permissions p
       left join RolePermissions rp on p.id=rp.PermissionId
       where rp.PermissionId is null
    ) p

查找3个表之间的缺失值

1 个答案: