使用UNION进行SQL多表查询，如何获取表名

Question

I have the following table structure. One table EQUITIES and a table for each row in this table.

EQUITIES table:
id instrument

and tables for every instrument with are all similar to this: Tables named like EE5367126893 (various names and the names are stored in equities table).

EE5367126893
id chg 

EDIT: My code is BAD. It somehow gets me wrong results and i can't seem to find an error.

<?
//CREATION OF TOP MOVERS
include('connect.php');
$sql = "SELECT * FROM equities";     

$result = mysql_query($sql) or die(mysql_error());

$instruments = array();
while ($row = mysql_fetch_array($result)) {
    array_push($instruments, $row["instrument"]);
}
$i=0;
foreach($instruments as $instrument) {
    $sqlx .= "(SELECT id, chg, vol, '$instrument' as name FROM ".$instrument." ORDER BY id DESC LIMIT 1)";
    if ($i<count($instruments)-1){
            $sqlx .= " UNION ";
            $i++;
    }
}
$gsql = $sqlx;
$lsql = $sqlx;
$vsql = $sqlx;

//Gainers
$gsql .= " ORDER BY chg DESC LIMIT 3";
$gresult = mysql_query($gsql) or die(mysql_error());
while ($grow = mysql_fetch_array($gresult)) {
    $g[$grow['name']] = $grow['chg'];;
}
print_r($g);
//losers
$lsql .= " ORDER BY chg ASC LIMIT 3";
$lresult = mysql_query($lsql) or die(mysql_error());
while ($lrow = mysql_fetch_array($lresult)) {
    $l[$lrow['name']] = $lrow['chg'];;
}
print_r($l);
//most volume
$vsql .= " ORDER BY vol DESC LIMIT 3";
$vresult = mysql_query($vsql) or die(mysql_error());
while ($vrow = mysql_fetch_array($vresult)) {
    $v[$vrow['name']] = $vrow['vol'];;
}
print_r($v);
?>

It got me results:

Array
(
    [LV0057869] => 0.68
    [EE310054309] => 0.00
    [EE3100034553] => -5.03
)
Array
(
    [LV0054359] => -0.84
    [LT0000543337] => -3.83
    [LT00453127375] => -4.03
)
Array
(
    [EE310054334653] => 791
    [EE3100003609] => 58538
    [LT000543337] => 33240
)

Its pretty obvious that I'm not getting the the highest, lowest or values with most vol (as -0.84>-5.03).It looks like random values got locked with this query. Where's the catch? Im pretty sure theres something bad with my sql query...

Answer 1

You can add name to select

SELECT id, chg, 'table_name or instrument_name' as inst_name from ...

Example:

$sqlx .= "(SELECT id, chg, '$instrument' as name FROM ".$instrument." ORDER BY id DESC LIMIT 1)";

It seems that vol has got VARCHAR type and rows are sorted by chars not by integers. Could you provide your table scheme?