title: Bring only one line in subquery
body: <p>I'm am doing a SELECT query, that bring back a car, and some of its pieces it need to repair.</p>
  
  <p>So I'm doing linke this : </p>
  
  <pre><code>SELECT id_car, concat((select pi.name_piece from t_piece pi LEFT JOIN t_piece_car pc on pc.id_piece = pi.id_piece where pc.id_car = 222), ',') as listPiece
  from car 
  where id_car = 222
  </code></pre>
  
  <p>piece contains all possible pieces.
  piece_car is a link between my car and piece. So it contains all pieces my car needs.</p>
  
  <p>The problem here is, the subquery bring more than one line. 
  I tried to concat inside the subquery, but nothing better.
  My car need 3 pieces, so it bring back 3 lines.
  I have to bring back one line, like this : </p>
  
  <p>'piece1, piece2, piece3' as listPiece</p>
  
  <p>But I always got 3 lines.</p>
  
  <p><strong>This is the subQuery that need to bring back only one line, with a concat of all the pieces names of my car, not the principal query.</strong></p>
  
  <p><strong>UPDATE : Finally found another question here :</strong> </p>
  
  <p><a href="https://stackoverflow.com/a/1076237/1439453">https://stackoverflow.com/a/1076237/1439453</a></p>
  
  <p>Considering, that my answer is not the same that in this question, I don't really know if it's needed to let this question open, but necessary to let exists.</p>
  
  <p>How can I do this.</p>
  
  <p>Thank you.</p>