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In performance wise distinct is good or group by is good?
eg:select name from emp group by name;
select distinct name from emp;
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Answer Posted / selvaraj.v
In SQL Server 2000:
-------------------
A DISTINCT and GROUP BY usually generate the same query
plan, so performance should be the same across both query
constructs. GROUP BY should be used to apply aggregate
operators to each group. If all you need is to remove
duplicates then use DISTINCT. If you are using sub-queries
execution plan for that query varies so in that case you
need to check the execution plan before making decision of
which is faster.
Example of DISTINCT:
--------------------
Query:
select DISTINCT Book_Title,COUNT(*) from bookdetails
Answer:
Server: Msg 8118, Level 16, State 1, Line 1
Column 'bookdetails.Book_Title' is invalid in the select
list because it is not contained in an aggregate function
and there is no GROUP BY clause.
Example of Group By:
--------------------
Query:
select Book_Title,COUNT(*) from bookdetails group by
Book_Title
Answer:
ASP 1
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In this Answer, the VB.NET is Duplicate, it having this
table in 3 times.
| Is This Answer Correct ? | 5 Yes | 3 No |
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