What is the difference between in and exists.
Ex: select * from emp where empno in(....) and
select * from emp where empno exists(....)

What is the difference between a Join and Union and Union
and UnionAll.

Answer Posted / shafiq...

When you use IN operator it will scan all the row in table
to check and Exists means when its find the data stop
execute to check further row.

Join- to join matching data from two or more table.
Union- Retrive matching data from both table.
UnionAll- Retrive matching as well as unmatched data from
both data.

hope this is clear

Is This Answer Correct ?    19 Yes 6 No



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