Update query with conditional?

I'm not sure if this possible. If not, let me know.

I have a PDO mysql that updates 3 fields.

$update = $mypdo->prepare("UPDATE tablename SET field1=:field1, 
                                                field2=:field2, 
                                                field3=:field3 
                                            WHERE key=:key");

But I want field3 to be updated only when $update3 = true; (meaning that the update of field3 is controlled by a conditional statement)

Is this possible to accomplish with a single query?

I could do it with 2 queries where I update field1 and field2 then check the b开发者_开发百科oolean and update field3 if needed in a separate query.

//run this query to update only fields 1 and 2
$update_part1 = $mypdo->prepare("UPDATE tablename SET field1=:field1, 
                                                      field2=:field2
                                                  WHERE key=:key");

//if field3 should be update, run a separate query to update it separately
if ($update3){
  $update_part2 = $mypdo->prepare("UPDATE tablename SET field3=:field3 
                                                    WHERE key=:key");
}

But hopefully there is a way to accomplish this in 1 query?

You don't need to do multiple queries. Why don't you just structure your query string based on that conditional, and after that just pass it to your DB adapater for execution ? It could be as follow:

    $pdo = new PDO($dsn, $user, $password);

    $sql = "UPDATE table SET columnname1=:field1, columname2=:field2";

    if ( $update ) $sql .= ",columname3=:field3";

    $sql .= " WHERE key=:key";

    $stmt = $pdo->prepare($sql);
    $stmt->bindParam(":key", $key, PDO::PARAM_INT);
    $stmt->bindParam(":field1", $field1, PDO::PARAM_STR);
    $stmt->bindParam(":field2", $field2, PDO::PARAM_STR);

    if($update) $stmt->bindParam(":field3", $field3, PDO::PARAM_STR);

    $stmt->execute();