As I asked in the drupal forum http://drupal.org/node/1393748 (no answers..) I have an issue with a db_select query.

It seems that addExpression "GROUP_CONCAT" and "HAVING" is causing an issue.

PDOException: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'ATTO' in 'having clause': SELECT COUNT(*) AS expression FROM (SELECT 1 AS ...

<?php
$query = db_select("adm_f", "f");
    $query->fields("f", array("F_ID", "F_TIT", "F_TITOR", "F_DES", "F_ANN", "F_PAE", "F_REG", "F_IMG"));
    $query->addExpression("GROUP_CONCAT(t.TAG_DESC separator ', ')", 'ATTO');
    $query->leftJoin('adm_a', 'a', 'a.F_ID = f.F_ID');
    $query->leftJoin('adm_t', 't', 'a.TAG_ID = t.TAG_ID');
    $query->condition('t.TAG_TIP', 'code', '=');
    // other conditions..
    $query->groupBy('f.F_ID');
    $query->groupBy('f.F_TIT');
    $query->groupBy('f.F_TITOR');
    $query->groupBy('f.F_DESC');
    $query->groupBy('f.F_ANN');
    $query->groupBy('f.F_PAE');
    $query->groupBy('f.F_REG');
    $query->groupBy('f.F_IMG');

    // BUG ???
    if(trim($_GET['F_ATTO']) != '')
        $query->havingCondition('ATTO', '%'.trim($_GET['F_ATTO']).'%', 'LIKE'); 
    
$query = $query->extend('PagerDefault')->limit(10);
    // echo($query->__toString()); exit;
    // execute
    $rs = $query->execute();
?>

I solved the problem with a workaround, but I would like to use HAVING and not a second query...

Many thanks for your help!!