Nested select statement in mysql -my code doesn't work

here is my query

SELECT con_serial,column2,column3
 FROM
 (SELECT con_serial,column2,column3
 FROM big_table 
 WHERE ISNULL(contact1, '')+'#'+ISNULL(contact2, '')+'#'+ISNULL(contact3, '')+'#'+ISNULL(contact4, '')+'#'+ISNULL(contact5, '')
 LIKE '%' + '".$conserial."' + '%') AS a
 WHERE con_serial
IN('".$contact1."','".$contact2."','".$contact3."','".$contact4."','".$contact5."')

at the inner select i wish to get the rows which have this value $conserial in one of their 5 columns(contact1...contact5)

and the outer select to choose the rows from it that their column con_serial is one of the variables ($contact1...$contact5)

can anybody see what's wrong here?

Solution

Despite your new formulation, it remains very much unclear.
Nevertheless I'll try to give you an answer, based on what I can guess...

First here is how I'd reformulate your need:

you have some values in PHP variables: one $conserial and five $contact# where # is 1-5
the table structure contains at least these columns: con_serial, column2, column3, and five contact# where # is 1-5
you want to select rows where both (here is the most strange part of your need):
- at least one of the contact# columns matches the PHP $conserial value
- the con_serial column matches at least one of the PHP $contact# values

That said, note that you don't need to have two nested SELECT: you only want each row to satisfy two conditions, so they can be ANDed in the WHERE clause.

Based on that, your query should be:

$query = "
  SELECT con_serial, column2, column3
  FROM big_table
  WHERE con_serial IN ('$contact1', '$contact2', '$contact3', '$contact4', '$contact5')
  AND '$con_serial' IN (contact1, contact2, contact3, contact4, contact5)
";