SQL语句，求高手帮助！解决方案

--> 测试数据：[Permission]if object_id('[Permission]') is not null drop table [Permission]create table [Permission]([PID] varchar(4),[PName] varchar(4))insert [Permission]select 'P001','读取' union allselect 'P002','追加' union allselect 'P003','删除'--> 测试数据：[USER]if object_id('[USER]') is not null drop table [USER]create table [USER]([USERID] varchar(4),[USERNAME] varchar(6))insert [USER]select 'U001','赵用户' union allselect 'U002','钱用户' union allselect 'U003','孙用户'--> 测试数据：[PerAssign]if object_id('[PerAssign]') is not null drop table [PerAssign]create table [PerAssign]([PID] varchar(4),[USERID] varchar(4))insert [PerAssign]select 'P001','U001' union allselect 'P001','U002' union allselect 'P001','U003' union allselect 'P002','U002' union allselect 'P002','U003' union allselect 'P003','U002'SELECT C.USERID AS 用户ID,C.USERNAME AS 用户名,C.PID AS 权限ID,C.PName AS 权限名,CASE WHEN D.PName IS NULL THEN '否' ELSE '是'END AS 是否有权限 FROM(SELECT * FROM [USER] CROSS JOIN [Permission])CLEFT JOIN(SELECT A.PID,A.USERID,B.PName FROM [PerAssign] A LEFT JOIN [Permission] B ON A.PID=B.PID)D ON C.USERID=D.USERID AND C.PID=D.PID /* 用户ID    用户名    权限ID    权限名    是否有权限U001    赵用户    P001    读取    是U001    赵用户    P002    追加    否U001    赵用户    P003    删除    否U002    钱用户    P001    读取    是U002    钱用户    P002    追加    是U002    钱用户    P003    删除    是U003    孙用户    P001    读取    是U003    孙用户    P002    追加    是U003    孙用户    P003    删除    否*/