MySQL query with "not exists" takes too long <p>I have a table like this:</p> <p>u</p> <p>My query is </p> <pre><code>SELECT *, week (pdate,3) FROM pubmed where not exists (select 1 from screened where suser=86 and ssearch=pubmed.aid) order by pdate desc </code></pre> <p>Screened has only 30000 records, but the query takes several minutes. </p> <p>Pubmed.aid is the primary index.</p> <p>I think I have created all the indexes I can use. Any ideas?</p> <p>Thank you.</p>