I have a table like this:

```
// mytable
+----+---------+------------+
| id | id_post | code_table |
+----+---------+------------+
| 1  | 34523   | 1          |
| 2  | 3453    | 4          |
| 3  | 43434   | 2          |
| 4  | 54321   | 1          |
| 5  | NULL    | NULL       |
| 6  | 32411   | 2          |
| 7  | 42313   | 1          |
| 8  | 34242   | 2          |
+----+---------+------------+
//                    ^ all of my focus is on this column

```

Also I have this array:

```
$convert_code_name = array (
                        "1" => "Post1", 
                        "2" => "Post2", 
                        "3" => "Post3",
                        "4" => "Post4"  
                           );

```

Now **I want to create this**:

```
$query = "select * from post1
             union all
          select * from post2
             union all
          select * from post4";

          // there isn't "post3", because 3 isn't exist in the code_table column

```

How can I do that?

---

Here is **my try**:

```
// connect to database
$stm = $db->prepare('select * from mytable');
$stm->execute();
$result = $stm->fetch();

/* array_unique: removes duplicate values
   array_filter: removes "NULL" values */

array_filter(array_unique($result[code_table]), function($item) {
    return $item != 'NULL';
});

foreach($item as $numb){
    $query .= 'select * from'.$convert_code_name[$numb].'union all';
}

```

But I don't know why my code doesn't work, How can I do that?