title: what is the difference between an anti-join and an anti semi join?
body: <p>From <a href="http://www.dbspecialists.com/files/presentations/semijoins.html" rel="noreferrer">http://www.dbspecialists.com/files/presentations/semijoins.html</a></p>
  
  <blockquote>
    <p>An “anti-join” between two tables returns rows from the first table
    where no matches are found in the second table. An anti-join is
    essentially the opposite of a semi-join: While a semi-join returns one
    copy of each row in the first table for which at least one match is
    found, <strong>an anti-join returns one copy of each row in the first table
    for which no match is found</strong>.</p>
  </blockquote>
  
  <p>Isn't an anti semi-join instead of an anti-join the one which "returns one copy of each row in the first table for which no match is found"?</p>
  
  <p>If it is, what is the definition of an anti-join?</p>
  
  <p>Note that my question is at the general level of SQL, such as at the level of college text books on database concepts, not specific to a particular SQL RDBMS implementation</p>
  
  <p>Thanks.</p>