结果一样，为什么会报错？
LeetCode中的一道题
Employee 表包含所有员工信息，每个员工有对应的 Id，此外还有一列部门 Id。
我的解题思路是分别找出IT收入最高的前三名和sales收入最高前三名，然后将两个表合并。
Select a.* from (SELECT d.name as Department,e.name AS Employee,e.Salary from Employee e
join Department d on e.DepartmentId=d.id
where d.name='IT'
order by salary DESC
limit 3) as a
union select b.* from
(SELECT d.name as Department,e.name AS Employee,e.Salary from Employee e
join Department d on e.DepartmentId=d.id
where d.name='Sales'
order by salary DESC
limit 3) as b；
join Department d on e.DepartmentId=d.id
where d.name='IT'
order by salary DESC
limit 3) as a
union select b.* from
(SELECT d.name as Department,e.name AS Employee,e.Salary from Employee e
join Department d on e.DepartmentId=d.id
where d.name='Sales'
order by salary DESC
limit 3) as b；
输出的结果是一样的，但是为什么会报错？
#leetcode#
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