The Free On-line Dictionary of Computing (30 December 2018):

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.

   (1998-11-23)