sqlquery with self join questions

I have an "emp" table with below records

INSERT into emp(EmpId,开发者_开发知识库Emp name, ManagerId)
Values(1,A,2)
values(2,B,3)
values(3,C,4)
values(4,D,-)

How can i find the Employee who does not have a Manager ie in this case the result should be D.

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Typically it would be like this.

SELECT EmpId, [Emp Name], ManagerId
FROM Emp
WHERE ManagerId is Null 

Your example is

SELECT EmpId, [Emp Name], ManagerId
FROM Emp
WHERE ManagerId = '-'

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SELECT EmpId, Emp name, ManagerId
FROM Emp
WHERE ManagerId IS NULL (or ManagerId='-' in your example)