Re: CHAR or VARCHAR

Folks -

> On other DBMSes there could be a difference, especially if the DBMS
> has
> performance problems with variable-length fields.

For example ... MS-SQL Server 7.0 requires 2 extra bytes to store the
length of a string for VARCHAR.  Thus, CHAR(3) takes 3 bytes (roughly)
and VARCHAR(3) takes 5.  Thus, if you knew that 90% of a particular
field's entries were going to be the same length, you could save some
storage space, and some processing power on scans and joins, by using
CHAR instead of VARCHAR.  (FYI, SQL Server 7 still has an 8K row limit;
I'm not sure about SQL Server 2000).

Now, Tom, at what point do character values begin to be stored "outside
the table"?  This is something I want to avoid, having had some bad
experiences with pointers and DB corruption (although not with PGSQL).

-Josh Berkus


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