Answer Posted / somashekhar m

Union : The union operator combines the results of two or
more queries into a single result set. But no.of columns
must match in both/all the queries (and also the order)
which are used for union.
Union -- returns with no duplicate rows
Union all -- retruns with duplicate rows (No. of rows
returned = No. of rows in Query1 + No. of rows in Query 2)
Union is a set operator.
You cannot use the union operator within a create view
statement.

You cannot use the union operator on text and image columns.

You cannot use the for browse clause in statements
involving the union operator.

Joins: Joins are used to extract information from more than
one table based on the related column/coloums (PK and RFK)
any no. of rows can be retrived based on matching matching
colums. Different types of joins are Inner join=equi join=
join, outer join(Right outer join/right join, Left outer
join/ left join), Cross join, and full outer join/outer join

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