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Editorial Team
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Asked: 2026-05-15T20:05:38+00:00

select * from ContactInformation c where exists (select * from Department d where d.Id

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select * 
from ContactInformation c 
where exists (select * from Department d where d.Id = c.DepartmentId )

select * 
from ContactInformation c 
inner join Department d on c.DepartmentId = d.Id

Both the queries give out the same output, which is good in performance wise join or correlated sub query with exists clause, which one is better.

Edit :-is there alternet way for joins , so as to increase performance:-
In the above 2 queries i want info from dept as well as contactinformation tables

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1 Answer

  1. Editorial Team

    Generally, the EXISTS clause because you may need DISTINCT for a JOIN for it to give the expected output. For example, if you have multiple Department rows for a ContactInformation row.

    In your example above, the SELECT *:

    • means different output too so they are not actually equivalent
    • less chance of a index being used because you are pulling all columns out

    Saying that, even with a limited column list, they will give the same plan: until you need DISTINCT… which is why I say “EXISTS”

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