having some syntax issue with a PHP based MySQL query, how to add another "where" clause?

 } else {
    $sql = "update products 
                set products_quantity = '" . $qty . "', 
                    products_last_modified = '" .date("Y-m-d H:i:s")."' 
            where " . PRODUCT_ID . "= '" . $model_no . "'";

    $result = mysql_query($sql);      // this executes the sql
  }
 } 
}                                   // back up to process next item

// and finally, close the db and we are done.
tep_db_close();

?>

credit for code to original author for a open source plug in posted online, currently the query is updating a product record’s stock level WHEN the product ID passed to it matches and also sets the last modified date.

I am also trying to add another where clause whereby the sql query needs to also only perform the record update if "products_status = 1" this is another field in the MySQL database and I only want to update records where this flag is on 1 . I tried adding this line in but I am clearly messing up the syntax.

Please don’t laugh but I tried something like

    $sql = "update products 
                set products_quantity = '" . $qty . "', 
                    products_last_modified = '" .date("Y-m-d H:i:s")."' 
            where " . PRODUCT_ID . "= '" . $model_no . "' 
            AND " . products_status . "= '" . "'1" . "'";

and it didn’t work

>Solution :

I think you are 90% there. The general form of a WHERE clause is:

WHERE
   field_1 = 'some specific value' AND
   field_2 = 1233  -- also a specific value

The original code you have for your WHERE clause is:

           where " . PRODUCT_ID . "= '" . $model_no . "'";

It seems to me here that PRODUCT_ID is a variable that is containing the name of a field and $model_no is the value. Although, it is possible that I have that backwards.

The code you added was:

AND " . products_status . "= '" . "'1" . "'"

I’m not sure if products_status is a variable containing the name of a field, but I’m guessing it is. Now, in the rest of the line there is an issue. You have " '" . "'1" . "'" This would evaluate to ''1', which is one too many single quotes. If product_status is a varchar or similar, you just want "='1'" if it is a numeric type you want "=1".