Does the order of columns in an index matter?

Hi,
I have a table having composite index, five columns. (col1,col2,col3,col4,col5)
Currently , my index is beginning with the column which having low distinct values and so on.
( in my case the first column have 1 distinct values due to functional behavior ). the second column have 3 distinct values , the third column have many distinct value ( half of the table).
There are many DML queries on this table with different clauses.
Examples:
query 1 : where col1 =val1 and col2 = val2
query 2 : where (col3,col4) in ( select col1,col2 from another_table ) ( for this we can add col1 =val1 and col2 = val2)
My question is : what this best way to create index on this case ?
The order of columns on index depends on its distinct values?
Thanks

BIJGA wrote:
Hi,
I have a table having composite index, five columns. (col1,col2,col3,col4,col5)
Currently , my index is beginning with the column which having low distinct values and so on.
( in my case the first column have 1 distinct values due to functional behavior ). the second column have 3 distinct values , the third column have many distinct value ( half of the table).
There are many DML queries on this table with different clauses.
Examples:
query 1 : where col1 =val1 and col2 = val2
query 2 : where (col3,col4) in ( select col1,col2 from another_table ) ( for this we can add col1 =val1 and col2 = val2)
My question is : what this best way to create index on this case ?CREATE INDEX
The order of columns on index depends on its distinct values? yes
Handle:     BIJGA
Status Level:     Newbie (5)
Registered:     Aug 24, 2009
Total Posts:     66
Total Questions:     18 (14 unresolved)
I extend my condolences to you since you rarely get answers to your questions.

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sql>select count(*)
2    from a
3   where object_name = 'x'
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dw_owner.fp_dinn c,
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Gangadhar Reddy wrote:
Does it matter the order of first 2 tables?This question makes me really wonder. It's fairly easy to see how explain changes when using hints.
Your question indicates that you do not look at explain plans?
Then why are you asking about hints in the first place?
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In all cases you know exactly what you are doing.
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var j = 0;
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set @min=@min+1
end
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Regards,
Julie

Does the order of columns in an index matter?

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