how much index are reasonable on a table?

I have a table with about 25 colums. In my application, we have provided an
interface through which , search can be made on different column, either
alone or with combination of different columns.
Now there are about 10 columns , upon which search can be made, either
indicidually colum, or combined colums.
Now in order to have a fast search, I have to apply index on different
columns.
Is it ok to apply index on all the 10 columns that are used in search or
what else is the solution to have a quick search. I cant change Database
schema.examnotes (SOHAIL MALIK@.discussions.microsoft.com)
writes:
> I have a table with about 25 colums. In my application, we have provided
> an interface through which , search can be made on different column,
> either alone or with combination of different columns. Now there are
> about 10 columns , upon which search can be made, either indicidually
> colum, or combined colums.
> Now in order to have a fast search, I have to apply index on different
> columns.
> Is it ok to apply index on all the 10 columns that are used in search or
> what else is the solution to have a quick search. I cant change Database
> schema.
Not all indexes might be useful. Say for instance that one column
you can search for is a gender column. If the search is for "all males",
then that index will not help anyway.
If searching for "all" is not meaningful, you may to want to constrain
users by saying "you must include one of A, B, C, D or E in the search",
where A, B, C, D and E are the column on which you have indexes.
--
Erland Sommarskog, SQL Server MVP, esquel@.sommarskog.se
Books Online for SQL Server SP3 at
http://www.microsoft.com/sql/techin.../2000/books.asp|||so it means, i should apply index on all 10 columns, that are used in search
.
"Erland Sommarskog" wrote:

> examnotes (SOHAIL MALIK@.discussions.microsoft.com)
> writes:
> Not all indexes might be useful. Say for instance that one column
> you can search for is a gender column. If the search is for "all males",
> then that index will not help anyway.
> If searching for "all" is not meaningful, you may to want to constrain
> users by saying "you must include one of A, B, C, D or E in the search",
> where A, B, C, D and E are the column on which you have indexes.
> --
> Erland Sommarskog, SQL Server MVP, esquel@.sommarskog.se
> Books Online for SQL Server SP3 at
> http://www.microsoft.com/sql/techin.../2000/books.asp
>|||In addition to Erland's suggestions, look at my answer in the
"paralel-universe" post. ;)
ML|||SOHAIL MALIK (SOHAILMALIK@.discussions.microsoft.com) writes:
> so it means, i should apply index on all 10 columns, that are used in
> search.
Nah, what I tried to imply that you should investigate whether all these
indexes are meaningful, and particularly whether searching for all rows
is meaningful.
The result of this investigate could very well be that you should index
all ten columns. I don't the table, nor the data distribution, so I
cannot say.
Erland Sommarskog, SQL Server MVP, esquel@.sommarskog.se
Books Online for SQL Server SP3 at
http://www.microsoft.com/sql/techin.../2000/books.aspsql