Related Tables: Performance vs Elegance

We have a table that holds information on Buildings (quite a large table and with lots of fields). Normally each Building has one single street number associated with it, but in some situations it can have more than one.

Example: Building XPTO, 1 - 3 - 5 (street numbers 1, 3 and 5)

Whe have a second table (Street_Number) wich holds one entry for each street number. In the above example the table would include 3 entries:

	XPTO	1
	XPTO	3
	XPTO	5

OUR QUESTION: Since say, 90% of the Buildings only have one Street number, would it be more reasonable to include an extra field in the table Buildings, to hold the first street number, and another field to indicate if the number is/is not unique. If the street number is not unique, then we would search the Street_Number table to obtain the remaining values. This way the Street_Number table would include entries only for street numbers of 10% of the buildings.

Is this the correct way of doing it ?

The alternative would be to store all the street numbers for all buildings in the Street_Number table. When querying building information (including street number), searching the Street_Number table is therefore always mandatory...

Thank you in advance for any comments or tips,

Miguel Received on Wed Mar 19 1997 - 00:00:00 CST