When you select from more than one table without defining a join condition that maps the rows of one table to the rows of another table, you create a Cartesian product, which is generally an expensive result that includes every combination of records between the tables, and usually has no real meaning.
SQLWizard supports automatic joining of columns in three cases. Note that the third case is not usually a very good method for automatically joining tables. Frequently, there are like column names that have no join relationship with each other. It is recommended that you use the first two options whenever possible, or manually define joins.
To define an automatic join, click the Current Query Options command from the Query menu to display the Query Options dialog box, and check the desired auto join methods. Alternatively, click the Auto Join command from the Query menu to display a submenu of the desired methods. Note that if you change the auto join options after having selected your tables, you are asked if you want to apply the join criteria after the fact.
The three cases on which automatic joins can be performed between the columns of two tables are when: