Define join and outer join, Database Management System

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Define Join and Outer Join and differentiate between them.     

Ans: Join - It generates all the combinations of tuples from two relations which satisfy a join condition.  Outer Join - If there are any type of values in one table that do not have corresponding value(s) in the other, in an equi-join which will not be selected. Such rows can be forcefully selected through using the outer join. The corresponding columns for that row will comprise NULLs. There are in fact three forms of the outer-join operation: left outer join, right outer join and full outer join.


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