具有多个动态条件的SQL查询选择

Question

I want to perform a SELECT query with conditions which are filled dynamically.

if($_POST['a']=='true'){
    $a = 'a,';
    $a_where = 'a >0';
}
if($_POST['b']=='true'){
    $b = 'b,';
    $b_where = 'b >0';
}
if($_POST['c']=='true'){
    $c = 'c,';
    $c_where = 'c >0';
}

Than i was tring to make WHERE

$where = 'WHERE '.$a_where.' OR '.$b_where.' OR '.$c_where;

And query

$query = mysql_query('SELECT id,'.$a.$b.$c.'date FROM t_name '.$where.' ORDER BY date DESC');

Problem is if b or a is not POST than i have error in query. Actualy only WHERE clause is problem here.

Answer 1

Rather than building the as separate variables, it's easier to collect them as arrays, do this for both the column names and the parts of the where clause and then use implode() to build the full SQL...

$columns = [ 'id', 'date' ];
$where = [];
if($_POST['a']=='true'){
    $columns[] = 'a';
    $where[] = 'a >0';
}
if($_POST['b']=='true'){
    $columns[] = 'b';
    $where[] = 'b >0';
}
if($_POST['c']=='true'){
    $columns[] = 'c';
    $where[] = 'c >0';
}

$sql = 'SELECT '.implode(",", $columns).'
          FROM t_name 
          WHERE '.implode(" or ", $where).' 
          ORDER BY date DESC';