PHP和Mysql无法使用UNION获取表的名称

Question

if($result = mysql_query(
"SELECT `condition` FROM `table1` WHERE `id` = '1')
 UNION ALL
SELECT `condition` FROM `table2` WHERE `id` = '1')
 UNION ALL
SELECT `condition` FROM `table3` WHERE `id` = '1')"
){ 
      $num = mysql_num_rows($result);
      for($i = 0;  $i < $num; $i++){     
        $table = mysql_field_table($result, $i);
        echo  $table.' cond: '.mysql_result($result, $i, 'condition').', ';
      }
}

Here I can get results of query(condition), but I do also want to get the tables' names, in order to know to which table the result belongs, I tried it: mysql_field_table($result, $i), but it does not return anything. So please help me to get name of table, thank you in advance.

Answer 1

You have a set of calculated columns so there's no source table you can trace back. You need to add the information yourself:

SELECT `condition`, 'table1' AS source
FROM `table1`
WHERE `id` = '1'

UNION ALL

SELECT `condition`, 'table2'
FROM `table2`
WHERE `id` = '1'

UNION ALL

SELECT `condition`, 'table3'
FROM `table3`
WHERE `id` = '1'