MYSQL variables in php query

Question

The solution to this problem might be a simple over sight of mine.

I am trying to run a MYSQL query stored as a string in PHP. The query runs fine using DBM tool like Navicat but returns false in my PHP development enviorment. Is there something I've over looked?

SET @running_sum = 0;

SELECT
    TID,
    SumTotal,
    T.`Freight`,
    T.`Insurance`,
    T.`Discount`,
    CONCAT(
        '$',
        FORMAT(
            @running_sum :=@running_sum + SumTotal + T.`Freight` + T.`Insurance` - T.`Discount`,
            2
        )
    ) AS 'Running Total'
FROM
    (
        SELECT
            TID,
            SUM(Quantity * UnitNetValue) AS SumTotal,
            T.`Freight`,
            T.`Insurance`,
            T.`Discount`
        FROM
            Transactions T
        JOIN `Transactions_Products` P ON T.TransactionID = P.TID
        WHERE
            (
                T.TemplateName = ''
                OR T.TemplateName IS NULL
            )
        AND T. STATUS = 1
        GROUP BY
            TransactionID

    ) AS T;

I am executing the query like this;

$result = mysql_query($this->query);

$this->query is a string which holds the above query, as it is displayed to you above.

Solution 1

The problem is mysql_query() doesn't support multiple queries. Your SET @running_sum = 0; is considered a separate query and so you'll have to execute that first:

$result1 = mysql_query("SET @running_sum = 0;");

$result2 = mysql_query($this->query); // <-- without the SET ... query

From the Manual:

mysql_query() sends a unique query (multiple queries are not supported)

---

Side note: The mysql_* library is deprecated, it is recommended to upgrade to a modern MySQL library such as PDO or MySQLi.

Solution 2

There is also possible to use multi_query method instead of query of MySQLi:

$query = "SET @running_sum = 0; SELECT ...";
$db_link->multi_query($query);

Solution 3

put variable like this. i guess it should work.

 mysql_query("SELECT @i:=0");
 mysql_query("UPDATE table_name SET id = @i:=@i+1");

Comments

[David.LPower]

Thank you for your help MrCode. It is much appreciated. I will update my code to take this into account.

[Ariel]

I'm sorry, I misread it. I've deleted my comment. Delete yours too and we can pretend I never said anything. Sorry.

[Paul]

Please also be aware of the security consideration when using mysqli_multi_query() to send multiple queries at once. With mysqli_multi_query() you open yourself to injected queries like "; DROP DATABASE". php.net/manual/en/mysqli.quickstart.multiple-statement.php