怎么实现如下设计

[tangyuanjian]

plan id,buyerId,operId,deptId
user id ,userId,userName
dept id deptId,deptName
根据上面的设计，要得到下面的结果集合
id ,buyerName,operName,deptName
其中buyerId,operId 不一样,但都可以通过user表查到名字?

[Bishop]

SELECT * FROM (SELECT plan.id,userName AS buyerName FROM plan LEFT JOIN user ON buyerId=userId) t1 NATURAL JOIN (SELECT plan.id,userName AS operName FROM plan LEFT JOIN user ON operId=userId) t2 NATURAL JOIN (SELECT plan.id,deptName FROM plan NATURAL dept USING(deptId)) t3;

[Bishop]

不好意思，上面打错了，更正如下：

SELECT * FROM (SELECT plan.id,userName AS buyerName FROM plan LEFT JOIN user ON buyerId=userId) t1 NATURAL JOIN (SELECT plan.id,userName AS operName FROM plan LEFT JOIN user ON operId=userId) t2 NATURAL JOIN (SELECT plan.id,deptName FROM plan LEFT JOIN dept USING(deptId)) t3;