Re: JOIN query too slow

[Peter Brawley]

Queries are much easier to develop, debug & maintain when joins use aliases and are written using explicit join syntax, ie the base query you show is ...

SELECT 
  p.IdPersona AS id,
  p.NIF AS DNICIF,
  p.Nombre AS Nombre,
  p.Apellidos AS Apellidos,
  p.Email AS Email,
  p.Telefono AS OtrosDatos 
FROM 
  Personas p, 
  Personas_experiencias AS e0 ON p.IdPersona  = e0.IdPersona
  Personas_experiencias AS e1 ON e0.IdPersona = e1.IdPersona
  Personas_experiencias AS e2 ON e1.IdPersona = e2.IdPersona
  Personas_experiencias AS e3 ON e2.IdPersona = e3.IdPersona

As EXPLAIN shows, the base query should execute quickly. If that takes 90 secs on your system, something's seriously amiss with your configuration. You might start with the hints at http://dev.mysql.com/doc/refman/5.5/en/optimizing-queries-myisam.html. Or is it the query with extra clauses that takes 90 secs? In that case, let's see those clauses.