6. Using JoinDefs in QBF : Automatic Joins
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Automatic Joins
Columns involved in a join need not have the same name, just the same data type and common values. However, when tables specified in a join have columns with the same name and data type, those columns automatically become the join column. This is known as an automatic, default, or natural join. QBF displays a list of join columns on the JoinDef Specification frame, described later in this chapter. You can specify different columns as the join columns or remove columns from the join columns list. For more information, see How Columns Are Joined (see page How Columns Are Joined).
Keep in mind that when two tables have multiple join columns, all the data values in each join column must be identical for a query to return that row of data. For this reason, you must delete unneeded joins.