What is the query to select empname and his managername from an emp table?
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This sounds like another homework question. However, it is also probably the most common example of a self-join ever devised. Everybody uses this example, and it's real easy to find on the Web, so there's no reason why TechTarget shouldn't also publish it.
select e.empname , m.empname as managername from emp as e left outer join emp as m on m.empid = e.managerid
Whenever you join a table to itself, use table aliases to distinguish the "copies" of the table. (The optimizer might not actually use two "copies" of the table, but it is convenient to think of it as working that way.)
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