How to define and perform CRUD on custom entities in drupal - php

Question

I've built an application to run on the client side (JavaScript & HTML) which needs to access and updated data on a server. It has a schema which consists of 5 tables. I've defined exactly what they should look like in JSON. I want these to be available as a JSON service served from a Drupal module. I understand how to use drupal_json_output to provide the results. I just can't find a simple way to ensure the database table is created for them and then to add and remove items from it. I'd like to maintain Drupal's independence from the underlying database. I don't need any search functionality, forms functionality etc. I just want to use Drupal's Database Abstraction.
At the moment I've tried the following in my install file:
/**
* Implements hook_schema
*/
function rcsarooms_schema(){
$schema = array();
$schema['rcsarooms'] = array(
'description' => 'Stores the structured information about the rooms and staircases.',
'fields' => array(
'ID' => array(
'type' => 'varchar',
'length' => 10,
'not null' => TRUE,
'description' => 'Primary Key: used in the URLs to identify the entity.'
),'Name' => array(
'type' => 'varchar',
'length' => 200,
'not null' => TRUE,
'description' => 'The name used for links in the navigation menues.'
),'ParentID' => array(
'type' => 'varchar',
'length' => 10,
'not null' => TRUE,
'description' => 'The ID of the parent element or "Root" if this is a root element'
),'Type' => array(
'type' => 'varchar',
'length' => 15,
'not null' => TRUE,
'description' => 'page, staircase, house, room or special'
),'BathroomSharing' => array(
'type' => 'int',
'description' => 'The number of people the bathroom is shared with (0 for unknown)'
),'RentBand' => array(
'type' => 'int',
'description' => 'The ID of the rent band the room is in.'
),'Floor' => array(
'type' => 'int',
'description' => 'The floor number (0 is courtyard level).'
)
),
'primary key' => array('ID')
);
return $schema;
}
And the following in my module file:
/**
* Implements hook_menu
*/
function rcsarooms_menu(){
$items['rcsarooms'] = array(
'page callback' => 'rcsarooms_callback',
'access callback' => TRUE,
'type' => MENU_CALLBACK
);
return $items;
}
function rcsarooms_callback(){
drupal_json_output(db_query("SELECT * FROM {rcsarooms}"));
drupal_exit();
return;
}
This gives the following error when I attempt to navigate to rcsarooms:
PDOException: SQLSTATE[42S02]: Base table or view not found: 1146 Table 'db.rcsarooms' doesn't exist: SELECT * FROM {rcsarooms}; Array ( ) in rcsarooms_callback()

Answer 1

You're probably looking for hook_schema() which Drupal will use to create your custom tables when you install your module. It goes in the mymodule.install file.
The Schema API will tell you everything you need to know about data types etc.
For adding/removing items from the database use the db_insert(), db_update() and db_merge() functions