A database operation that combines some or all records from two or more tables, such as an equi-join, outer join, or self-join. Generally, a join refers to an association between a field in one table and a field of the same data type in another table. You create a join with an SQL statement.
When you define a relationship between two tables, you create a join by specifying the primary and foreign table fields. When you add a table to a query, you need to create a join between appropriate fields in the SQL statement that defines the query.