title: Skipping lines in update query
body: <p>I've created an update query to update lines in the Partij table with data from the Bestel table. There's one thing missing in this query and hopefully someone can help me :)</p>
  <pre><code>update partij
  set Inkprijs1 = (
    select bestel.inkoopprijs
    from bestel
    where partij.levcod= bestel.levcod
    and partij.scancode = bestel.scancode
    and bestel.devisie = 'HARDWA')
  ,inkprijs2 = (
    select bestel.prijs
    from bestel
    where partij.levcod= bestel.levcod
    and partij.scancode = bestel.scancode
    and bestel.devisie = 'HARDWA')
  ,PRIJSGRP_1 = (
    select bestel.PRIJSGRP_1
    from bestel
    where partij.levcod= bestel.levcod
    and partij.scancode = bestel.scancode
    and bestel.devisie = 'HARDWA')
  ,PRIJSGRP_2 = (
    select bestel.PRIJSGRP_2
    from bestel
    where partij.levcod= bestel.levcod
    and partij.scancode = bestel.scancode
    and bestel.devisie = 'HARDWA')
  
  where devisie = 'TESTHW'
     ;
  </code></pre>
  <p>I want to skip lines for the Partij update function when they don't excist in the table Bestel. When there are lines in the Partij tabel (with devisie TESTHW) without matching values the shouldn't get updatet at all.</p>
  <p>Hopefully someone can help me out! Thanks in advance</p>