Re: Number of Columns in a Table & SQL Performance ?
- From: Greg Rahn <greg@xxxxxxxxxxxxxxxxxx>
- To: VIVEK_SHARMA@xxxxxxxxxxx
- Date: Mon, 9 Mar 2009 14:22:25 -0700
First I have to ask myself, what (good) relational database design for
an OLTP system would lead normalized tables having 200 columns.
Second, I would think about buffer cache efficiencies. The wider the
table the less rows that fit in a block. Given that most OLTP
applications rarely need access to all the columns in a table it would
seem to me that having a 200, let alone 400 column table would lead to
having lots of data in the buffer cache that is not used and thus
result in either a reduced buffer cache efficiency (causing more than
desired physical I/O) or having to compensate by having a very large
db cache full of rows whose columns are not accessed.
Perhaps you could share what are the perceived benefits from merging
the two tables?
On Mon, Mar 9, 2009 at 6:19 AM, VIVEK_SHARMA <VIVEK_SHARMA@xxxxxxxxxxx> wrote:
> Does the number of columns in a table affect the performance of
> SELECT/INSERT/UPDATE in OLTP Transactions.
>
> If so, why?
>
> NOTE - Merge of 2 existing tables each has 200 columns approx into a single
> Table is being planned..
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