Creating conditional sql query

Question

I am having a problem getting a query to work (and also am questioning the security of the query).

  if(isset($_POST)){
        $sql = "SELECT * FROM members WHERE";

     if($_POST['FirstName_S'] !== ''){
        $sql .= " FirstName LIKE '%" . $_POST['FirstName_S'] . "%'";
     }
     if($_POST['LastName_S'] !== ''){
        $sql .= " OR LastName LIKE '%" . $_POST['LastName_S'] . "%'";
     }
     if($_POST['Firm_S'] !== ''){
        $sql .= " OR Firm LIKE '%" . $_POST['Firm_S'] . "%'";
     }
     if($_POST['Country_S'] !== ''){
        $sql .= " OR Country LIKE '%" . $_POST['Country_S'] . "%'";
     }
     if($_POST['City_S'] !== ''){
        $sql .= " OR City LIKE '%" . $_POST['City_S'] . "%'";
     }
     if($_POST['State_S'] !== '' AND $_POST['State_S'] !== 'other'){
        $sql .= " OR State LIKE '%" . $_POST['State_S'] . "%'";
     }
  }

Obviously, if FirstName_S is undefined, the query breaks saying "WHERE OR". It seems like it would have a logical fix, but I've been staring at it for a little too long.

Also, sql injection was brought up as a concern, and as a side-question, would sanitizing the input be enough? Or is this altogether bad practice?

Answer 1

  if(isset($_POST)){
        $sql = "SELECT * FROM members WHERE";

     if($_POST['FirstName_S'] !== ''){
        $sql .= "OR FirstName LIKE '%" . $_POST['FirstName_S'] . "%'";
     }
     if($_POST['LastName_S'] !== ''){
        $sql .= " OR LastName LIKE '%" . $_POST['LastName_S'] . "%'";
     }
     if($_POST['Firm_S'] !== ''){
        $sql .= " OR Firm LIKE '%" . $_POST['Firm_S'] . "%'";
     }
     if($_POST['Country_S'] !== ''){
        $sql .= " OR Country LIKE '%" . $_POST['Country_S'] . "%'";
     }
     if($_POST['City_S'] !== ''){
        $sql .= " OR City LIKE '%" . $_POST['City_S'] . "%'";
     }
     if($_POST['State_S'] !== '' AND $_POST['State_S'] !== 'other'){
        $sql .= " OR State LIKE '%" . $_POST['State_S'] . "%'";
     }

    $sql=str_replace("WHERE OR","WHERE",$sql);   // quick dirty fix

  }

Ofcourse you'd need to sanitize the input, but since you didn't mention which MySQL API you use, I did not add any sanitization functions yet. You can look at http://php.net/mysqli_real_escape_string

Answer 2

do it other way as follow

if(isset($_POST)){
        $sql = "SELECT * FROM members WHERE";

     if($_POST['FirstName_S'] !== ''){
        $sql_arr[]=" FirstName LIKE '%" . $_POST['FirstName_S'] . "%'";

     }
     if($_POST['LastName_S'] !== ''){
        $sql_arr[]= " LastName LIKE '%" . $_POST['LastName_S'] . "%'";
     }
     if($_POST['Firm_S'] !== ''){
        $sql_arr[]= " Firm LIKE '%" . $_POST['Firm_S'] . "%'";
     }
     if($_POST['Country_S'] !== ''){
        $sql_arr[]= " Country LIKE '%" . $_POST['Country_S'] . "%'";
     }
     if($_POST['City_S'] !== ''){
        $sql_arr[]= " City LIKE '%" . $_POST['City_S'] . "%'";
     }
     if($_POST['State_S'] !== '' AND $_POST['State_S'] !== 'other'){
        $sql_arr[]= " State LIKE '%" . $_POST['State_S'] . "%'";
     }
     if(!empty($sql_arr)){
       $sql.=implode(' OR ',$sql_arr);
}

  }

Answer 3

The quick fix is to add 1=1 to your query, so your query ends with WHERE 1=1 . That allows you to be free to append any number of OR something to your query, without being concerned with omitting the OR on the first one.

(That 1=1 predicate doesn't cause any problem; that will be evaluated at parse time, and doesn't appear in the execution plan.)

As to SQL Injection, yes, this code is susceptible. If you are using mysql interface, then sanitize the post variables with mysql_real_escape_string function. If you are using mysqli or PDO (and you should be), then use parameterized queries.

Answer 4

$stmt = $dbConnection->prepare('SELECT * FROM members WHERE FirstName LIKE ? OR LastName LIKE ? OR FIRM LIKE ? OR Country LIKE ? OR CITY LIKE ? OR STATE LIKE ?');


if($_POST['FirstName_S'] !== ''){
  $stmt->bind_param('FirstName', '%'.$_POST['FirstName_S'].'%');
} else {
  $stmt->bind_param('FirstName', '%');
}

… // do this for all your parameters

$stmt->execute();

Answer 5

I think this could help you:

if(isset($_POST)){
    $sql = "SELECT * FROM members";

 if($_POST['FirstName_S'] !== ''){
    $sql .= " WHERE FirstName LIKE '%" . $_POST['FirstName_S'] . "%'";
 }
 else {
   $sql .= " WHERE FirstName LIKE '%'";
 }
 if($_POST['LastName_S'] !== ''){
    $sql .= " OR LastName LIKE '%" . $_POST['LastName_S'] . "%'";
 }
 if($_POST['Firm_S'] !== ''){
    $sql .= " OR Firm LIKE '%" . $_POST['Firm_S'] . "%'";
 }
 if($_POST['Country_S'] !== ''){
    $sql .= " OR Country LIKE '%" . $_POST['Country_S'] . "%'";
 }
 if($_POST['City_S'] !== ''){
    $sql .= " OR City LIKE '%" . $_POST['City_S'] . "%'";
 }
 if($_POST['State_S'] !== '' AND $_POST['State_S'] !== 'other'){
    $sql .= " OR State LIKE '%" . $_POST['State_S'] . "%'";
 }

}

and for the SQL injections, you can check General_Twyckenham comment.

Answer 6

You could compose the WHERE command based on what parameters is entered...

if(isset($_POST)){
    $sql_where = '';
    $sql = "SELECT * FROM members ";

    if($_POST['FirstName_S'] !== ''){
        $sql_where .= (($sql_where != '')?('OR '):(''))." FirstName LIKE '%" . $_POST['FirstName_S'] . "%' ";
    }
    if($_POST['LastName_S'] !== ''){
        $sql_where .= (($sql_where != '')?('OR '):(''))." LastName LIKE '%" . $_POST['LastName_S'] . "%' ";
    }
    if($_POST['Firm_S'] !== ''){
        $sql_where .= (($sql_where != '')?('OR '):(''))." Firm LIKE '%" . $_POST['Firm_S'] . "%' ";
    }
    if($_POST['Country_S'] !== ''){
        $sql_where .= (($sql_where != '')?('OR '):(''))." Country LIKE '%" . $_POST['Country_S'] . "%' ";
    }
    if($_POST['City_S'] !== ''){
        $sql_where .= (($sql_where != '')?('OR '):(''))." City LIKE '%" . $_POST['City_S'] . "%' ";
    }
    if($_POST['State_S'] !== '' AND $_POST['State_S'] !== 'other'){
        $sql_where .= (($sql_where != '')?('OR '):(''))." State LIKE '%" . $_POST['State_S'] . "%' ";
    }
    $sql .= (($sql_where != '')?('WHERE '.sql_where):(''));
}