• Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint
Share this Page URL
Help

Chapter 8. Queries > Inner Versus Outer Joins

Inner Versus Outer Joins

There are both inner joins and outer joins. Inner joins, which are also known as equi-joins, are by far the most common. All the queries you have done used an inner join. An inner join retrieves records only when there are equal values (that is, matching data) in the common field in the tables. As you saw, if you have suppliers in one table and merchandise in another, and a common SupplierID in both, you can use an inner join to create a query that matches merchandise data with supplier data. When you create a multitable query, an inner join is the default. If you want to create queries in which only records with matching data are retrieved, you don't have to worry what type of join you're using.

Introducing Outer Joins

What are outer joins? In an outer join, all the records from one table and only those records from the other table in which there's matching data are retrieved. Because all the records are retrieved from one table, you can find which of them don't have matching records in the other table.


PREVIEW

                                                                          

Not a subscriber?

Start A Free Trial


  
  • Creative Edge
  • Create BookmarkCreate Bookmark
  • Create Note or TagCreate Note or Tag
  • PrintPrint