Multi-column Index vs Single Column Indexes

[Sonny]

Hi,

Would like to know the performance differenece between Multi-column
Index vs Single Column Indexes. Let's say I have a table with col1,
col2, col3 along with a primary key column and non-indexed columns.
In queries, I will use col1, col2, and col3 together and some times
just one or two of these three columns. My questions is, should I
create one index contains col1, col2, and col3, or create 3 seperated
columns. I.e. each column has its own index. Any performance
difference?

Thanks a lot.

[Alex Kuznetsov]

On Aug 7, 1:10 pm, Sonny <[e-mail]:

Hi,

Would like to know the performance differenece between Multi-column
Index vs Single Column Indexes. Let's say I have a table with col1,
col2, col3 along with a primary key column and non-indexed columns.
In queries, I will use col1, col2, and col3 together and some times
just one or two of these three columns. My questions is, should I
create one index contains col1, col2, and col3, or create 3 seperated
columns. I.e. each column has its own index. Any performance
difference?

Thanks a lot.

It depends on your workload. You need to try it out using the mix of
reads and writes similar to your actual activity.

Alex Kuznetsov, SQL Server MVP
http://sqlserver-tips.blogspot.com/