DRUPAL - Retrieve all nodes that were children in a Book and whose root parent was of a specific node type

book-table.sql

mlid 	int(10) unsigned	NO	PRI	0	
nid	int(10) unsigned	NO	UNI	0	
bid	int(10) unsigned	NO	MUL	0	

query-drupal.php

<?php

$query = db_select('book', 'b')->distinct();
$query->innerJoin('node', 'n', 'b.bid = n.nid');
$query->innerJoin('book', 'bb', 'b.bid <> b.nid');
$query->addField('b', 'nid');
$query->condition('n.type', 'project', '=');
$query->orderBy('b.nid');

query1.sql

SELECT b.nid
FROM book b INNER JOIN node n ON b.bid=n.nid
WHERE b.bid <> b.nid AND n.type = 'project' ORDER BY b.nid;

query2.sql

SELECT DISTINCT b.nid
FROM book b
INNER JOIN node n ON b.bid = n.nid
INNER JOIN book bb ON b.bid <> b.nid
WHERE n.type = 'project'
ORDER BY b.nid;