cartesian square

A Cartesian square is the linking of all elements of a data set, e.g. a database table, with all elements of another data set. The Cartesian square is an important phenomenon in database technology, because it is usually to be avoided.

If two tables are linked in a database, all records of the first table are linked to all records of the second table without an explicit linking rule. Two tables would thus produce resulting recordset with axb rows, where "a" is the row count of table 1 and b is the row count of table 2. For example, a table with 100 records and another with 200 records could potentially create a recordset with 20,000 records. Obviously, this can quickly create extremely large recordsets.

Cartesian square of addresses and locations

In order to control the amount of data, all links between database tables are made using a linking rule to ensure that only those links are created that are actually needed.

There are few cases where a Cartesian square is desired, for example when a table with the same default values is to be created for each month of the year.