How to select all the field in content type
If you don't mind my saying, you don't want to do that manually. Drupal has a rich API which you should use. 

The standard method to load a node and all of its fields/extra data, is node_load():

$node = node_load($nid);


If you're trying to avoid the overhead of the 'extra' (non-field) data, then you can use field_attach_load() along with a basic DB query to get a reasonable node object with all fields attached.

// Get base node data (aka 'properties')
$node = db_query('SELECT * FROM {node} WHERE nid = :nid', array(':nid' =&gt; $nid))-&gt;fetchObject();

// Attach the fields
field_attach_load('node', array($node));


It is possible, of course, to query the database manually for all of this data, but when the functionality has already been written for you there doesn't seem any point.