Multiple Alias names for a table

Can we have multiple alias names fo开发者_Go百科r a single table?

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Yes. You need to do this for a self join, for example f you have a table storing a hierarchy:

create table Foo (
    FooID int
   ,ParentFooID int
   ,[columns]
)

You can do a join to get the children of parents that satisfy a particular condition with a query like:

Select b.*
  from Foo a
  join Foo b
    on a.FooID = b.ParentFooID
   and [some condition filtering a]

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No, not on the same table, but you can select the same table twice and give each a different alias.

SELECT alias1.*, alias2.*
FROM mytable alias1, mytable alias2

This will then allow you to use the same table for a different purpose within a single query.