Ambiguous?

1) query foreach($varenr_inn_pa_lager as $vnr){ include('../../tilkobling.php'); $sql = "SELECT * FROM exan,dynamit WHERE varenr = '$vnr' LIMIT 1"; $resultat = mysql_query($sql, $tilkobling) or die(mysql_error()); 2) Result: Column 'varenr' in where clause is ambiguous 3) Tables in MySQL database mysql> SELECT * FROM exan; +------------+-------------+-------+----------+----------+-------------+ | leverandor | valgt_lager | un_nr | varenavn | varenr | kg_pa_lager | +------------+-------------+-------+----------+----------+-------------+ mysql> SELECT * FROM dynamit; +------------+-------------+---------------+--------+-------+---------------------+------------+-------------+ | leverandor | valgt_lager | type | dim_mm | un_nr | varenavn | varenr | kg_pa_lager | +------------+-------------+---------------+--------+-------+---------------------+------------+-------------+ 4) My question: What means with "ambiguous" here? Thanks. Karl