SQL Query Not Reading Variables

Question

My query below updates a record using variables to identify the data in the DB. I think my syntax is correct although it might be wrong. Also, I am absolutely sure that the variables have legitimate values in them. Why won't this query work?

UPDATE  `databasename`.`".$tablename."` SET  `stock` =  '".$f."' WHERE  `myerspark`.`item_id` ='".$g."' LIMIT 1

Thanks guys. Tom, yes I have tried that and it works fine. But it is frustrating because I echo all three variables at the end of the script and they all display legitimate values.

Hamish, how do I view these errors?

Jon_Darkstar, these variables are assigned in previous lines of code. Here is my entire code block:

//variables $f, $g, and $tablename assigned from POST variables in previous lines
mysql_select_db($database_Yoforia, $Yoforia);
mysql_query("UPDATE `yoforiainventory`.`".$tablename."` SET `stock` =  '".$f."' WHERE `".$tablename."`.`item_id` ='".$g."' LIMIT 1 ");
mysql_close($Yoforia);

echo ($f);
echo ($tablename);
echo ($g);

Again, when i echo these variables, they all come out with good values.

What error are you getting? Have you tried hard-coding the PHP variable values just to see that it executes fine? — Tom
– Tom, Commented Nov 19, 2010 at 0:45
Looks fine. What errors do you get from MySQL? They're usually pretty descriptive. — Hamish
– Hamish, Commented Nov 19, 2010 at 0:46
if you assign that query to a variable, what's the value of that variable after this line of code? another thing i would do is trying variables inside the string (variable parsing). — Mario
– Mario, Commented Nov 19, 2010 at 1:06

jon_darkstar · Accepted Answer · 2010-11-19 01:05:21Z

I'm kind of confused what belongs to SQL, what belongs to PHP, where that string comes from, etc. What you have might be fine (if there is a double quote in front and end that i dont see.

I'd probably write it like this:

$sql = "UPDATE databasename.$tablename SET stock = '$f' WHERE myerspark.item_id = '$g' LIMIT 1"
$res = mysql_query($sql, $conn).....

you can backtick more stuff (and/or do mysql_real_escape) for 'extra safety;, but that covers the idea.

What is myerspark? i dont see how it relates to the query, that is probably you're real meaningful error, whether there is a syntax error or not. If myerspark is a seperate table from tablename then you've got an issue here, maybe a JOIN you ought to have?

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