inner join

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Related to inner join: outer join

inner join

(Commonly "join", but see also "outer join") A relational database operation which selects rows from two tables such that the value in one column of the first table also appears in a certain column of the second table.

An example in SQL:

select * from A, B where A.x = B.y

The column names (x and y in this example) are often, but not necessarily, the same.
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In relational database management, to match one table (file) against another based on some condition creating a third table with data from the matching tables. For example, a customer table can be joined with an order table creating a table for all customers who purchased a particular product.

The default type of join is known as an "inner" join. It produces a resulting record if there is a matching condition. For example, matching shipments with receipts would produce only those shipments that have been received. On the other hand, an "outer" join using that example would create a record for every shipment whether or not it was received. The data for received items would be attached to the shipments, and empty, or null, fields would be attached to shipments without receipts.

A Simple Join
This example matches the sales table against the product table based on product number to derive the product description.
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This example uses an inner join because the records being sought are ones where there are both an NTEE1 code and an associated charitable industry name.
INNER JOIN combines only records from the tables whenever the values in the matching field are equal.
The FROM clause indicates that the Products table will be joined (INNER JOIN) with the Customers table; however, the join must be threaded through the Orders and Order Details tables.