Two separate database queries to relate separate tables with Drupal 7 module? - sql

Question

I am developing a custom module for a site I'm working on and have created the following code. This is my first module, so any ideas of what I could be doing better would be appreciate.
As it is, this module works perfectly for me. But, I want to optimize it and be sure that I fix shoddy code.
Thanks!
The function in question is as follows:
// Declared variables for future incrementation
$total=0;
$countOne=0;
$countTwo=0;
$countThree=0;
$countOld=0;
// Call the native global user object from Drupal
global $user;
$userID = $user->uid;
// Check for nodes of given type owned by current user
$sql = db_query("SELECT nid FROM {node} WHERE type = 'content_type' AND uid = " . $userID);
// Iteratively checks each node id against a custom Drupal field on a separate table
foreach ($sql as $record) {
// SQL query for all custom fields attached to the node id given above
$query = db_query("SELECT * FROM {field_birth} WHERE entity_id = " . $record->nid);
$result = $query->fetchObject();
// The unmodified birth format (Y-m-d 00:00:00)
$originalBirth = $result->field_date_of_birth_value;
// The sanitized birth format for comparison (Y-m-d)
$birth = date('Y-m-d', strtotime($originalBirth));
// The current date/time (Y-m-d)
$now = date('Y-m-d');
//Future dates (Y-m-d)
$one_year = date('Y-m-d', strtotime('+1 year', strtotime($birth)));
$two_years = date('Y-m-d', strtotime('+2 years', strtotime($birth)));
$three_years = date('Y-m-d', strtotime('+3 years', strtotime($birth)));
// A count of all records returned before logical statements
$total++;
// Logic to determine the age of the records
if($now < $one_year) {
$countOne++;
}
else if($now >= $one_year && $now < $two_years) {
$countTwo++;
}
else if($now >= $two_years && $now < $three_years) {
$countThree++;
}
else {
$countOld++;
}
My question is, can I avoid having two separate database queries to hit both tables? I am not really sure how to go about that. Also, am I doing things in a manner which will be resource intensive and highly inefficient? As I am not a programmer by trade, I am not certain when code is 'good'. I do want to try my best to make this good code though since it is a module for a website I hope will last a long time.
Thank you stackoverflow community!
EDIT: The code I got working thanks to Mike is as follows. If anyone has a similar question / problem hopefully this will help!
// Join field_birth_table to nodes of given type owned by current user
$sql = db_select('node', 'n');
$sql->join('field_birth_table', 'b', 'n.nid = b.entity_id');
$sql
->fields('b', array('field_birth_field_value', 'entity_id'))
->condition('n.type', 'content_type')
->condition('n.status', '1')
->condition('n.uid', $user->uid)
->addTag('node_access');
$results = $sql->execute();

Answer 1

You can use a left join between the node and field_birth table:
$query = db_select('node', 'n');
$query->leftJoin('field_birth', 'b', '(b.entity_id = n.nid AND b.entity_type = :node)', array(':node' => 'node'));
$query
->fields('b', array())
->condition('n.type', 'content_type')
->condition('n.uid', $user->uid)
$results = $query->execute();