tsql - 不存在的 TSQL 循环

Question

我有一个角色和权限表，其中包含一个名为 role_permissions 的连接表。

对于每个角色，如果该角色尚未拥有该权限，我想插入一个新权限。我的循环的问题是只有一行（角色）被更新。该循环似乎没有正确地重新评估每个循环上的子查询（它找到第一个没有权限的角色）

DECLARE @role_id INT

SET @role_id = (SELECT TOP 1 role_id FROM p_role_permissions WHERE NOT EXISTS (SELECT NULL FROM p_role_permissions WHERE permission_id = 57))

WHILE @role_id IS NOT NULL
BEGIN

INSERT INTO p_role_permissions (role_id, permission_id) VALUES(@role_id, 57)
-- does not appear to evaluate correctly (works only on the first loop)
SET @role_id = (SELECT TOP 1 role_id FROM p_role_permissions WHERE NOT EXISTS (SELECT NULL FROM p_role_permissions WHERE permission_id = 57))

END

Answer 1

好的，在这里做一些假设，但我相信你可以这样做：

获取没有权限 57 的角色：

INSERT INTO p_role_permissions (role_id, permission_id)
   SELECT
       rp.Id,
       57
   FROM
       (SELECT
            r.Id
         FROM roles as r
         LEFT OUTER JOIN p_role_permissions as rp
         ON r.Id = rp.Role_Id AND rp.Permission_Id = 57

         WHERE r.Id IS NULL) as nr

Answer 2

INSERT INTO p_role_permissions (role_id, permission_id) (SELECT role_id, 57 FROM p_role_permissions WHERE NOT EXISTS (SELECT NULL FROM p_role_permissions WHERE permission_id = 57))

Answer 3

你不需要循环。您可以在一个插入语句中执行此操作。

;WITH RolesToAdd
     AS (SELECT role_id
         FROM   p_role_permissions /*Would be better to use a roles table here */
         EXCEPT
         SELECT role_id
         FROM   p_role_permissions
         WHERE  permission_id = 57)
INSERT INTO p_role_permissions
            (role_id,
             permission_id)
SELECT role_id,
       57
FROM   RolesToAdd 

Answer 4

MERGE INTO p_role_permissions 
USING (SELECT DISTINCT roleid, 57 FROM p_role_permissions) AS src  
ON (p_role_permissions)  
WHEN NOT MATCHED THEN   
    INSERT p_role_permissions (role_id, permission_id)
    VALUES (role_id, 57);