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POConverting mysql_query multi-table select command to PDO
 

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  1. POConverting mysql_query multi-table select command to PDO
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    <p>I have a couple of questions all pertaining to the same problem. I'm trying to update some of my MySQL connections/commands to PDO in order to mitigate SQL injections. I'm trying to convert this code:</p> <pre><code>$ulog = $_POST['driver']; $_SESSION['user_id'] = $ulog; $tablename_cc = "cc_".$ulog; $tablename_db = "db_".$ulog; $tablename_misc = "misc_".$ulog; $tablename_cash = "cash_".$ulog; $sql_cc = "SELECT * FROM " .$tablename_cc; $sql_db = "SELECT * FROM " .$tablename_db; $sql_misc = "SELECT * FROM " .$tablename_misc; $sql_cash = "SELECT * FROM " .$tablename_cash; $result_cc = mysql_query($sql_cc); $result_db = mysql_query($sql_db); $result_misc = mysql_query($sql_misc); $result_cash = mysql_query($sql_cash); </code></pre> <p>To the following code:</p> <pre><code>$tables = array($tablename_cc, $tablename_db, $tablename_misc, $tablename_cash); $A = count($tables); $result = array(); try { $STH = $DBH-&gt;prepare('SELECT * FROM :table'); $i = 0; while($i &lt; $A) { $STH-&gt;bindParam(':table', $tables[$i]); $STH-&gt;execute(); $result[$i] = $STH-&gt;fetchAll(); $i++; } } catch(PDOException $e) { echo $e-&gt;getMessage(); } </code></pre> <p>However, I keep getting a syntax error. The error goes away if I try it in the following way, but this way is not very useful to me because it does not avoid SQL injections.</p> <pre><code>try { $i = 0; while($i &lt; $A) { $STH = $DBH-&gt;query('SELECT * FROM ' .$tables[$i]); $result[$i] = $STH-&gt;fetchAll(); $i++; } } catch(PDOException $e) { echo $e-&gt;getMessage(); } </code></pre> <p>Although this last method works, from my understanding it does not help with mitigating SQL injection. And a secondary issue I'm running across is that sometimes these tables will not exist and my workaround for these issues in the old method was to do a small check:</p> <pre><code>$result_cc = mysql_query($sql_cc); if(mysql_num_rows($result_cc) != 0){} </code></pre> <p>However, this intermediate step seems to be gone in PDO, so I still need to figure out how to check for this.</p>
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    1. PTQuestion
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    1. USuser1562781
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      1. VTUpMod
    1. COYou cannot use `bindParam()` for [identifiers](http://dev.mysql.com/doc/refman/5.0/en/identifiers.html) (in your case, table names). `bindParam()` is only applicable for parameters. I would seriously advise you avoid variable table names and rethink your DB schema
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      1. USPhil
    2. COYou should not be creating identical tables for each of your "drivers". The driver should be a column in the 4 tables. That's the problem, and the reason the concept of binding table names doesn't exist.
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      1. USDan Grossman
    3. COThere is a table like that, but due to the way the data is being processed, there needs to be a table for each individual user/driver. These individual user tables are essentially intermediate steps (information inside them will get transferred out), but they're unfortunately necessary.
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      1. USuser1562781
 

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