[AccessD] Access 2010 Beta - Calculated fields

Asger Blond ab-mi at post3.tele.dk
Fri Feb 12 17:22:11 CST 2010


Hi group,
Just downloaded the Access 2010 Beta and observed that a new data type for fields was added: Calculated.
Knowing that this kind of denormalized field has been around in SQL Server for some time I thought it would be the same in A2K10.
Well: It's not!
In SQL Server a calculated field is not persisted, it's just a convenient way to pre-announce a calculation which will be used on the fly when querying the table. You can in fact persist the calculated values in SQL Server, but only if you create an index on the field - otherwise it's of course not persisted.
So I was astonished in A2K10 that I didn't have a choice whether to index this kind of field.
I then created a test db containing a table with two number-fields and one million records. Size of the db: 33 GB. To check I copied the db to a new db and added a calculated field to the table (trivial calculation: Field1 * Field2). And guess what? The size of the new db was double up+: 72 GB.
So please: stick to your old practice creating calculations only in queries, and don't ever use the new Calculated field type in Access 2010!

Asger





More information about the AccessD mailing list