Using XMLDB

(This page is in progress of writing and editing, intended for third-party module developers to help them switch to XMLDB.) Moodle1.7

What is XMLDB and how can it help you

XMLDB is a database format created to help developer from creating custom database schemas for different database system. It's like a database in XML format. Everywhere in Moodle now use XMLDB.

In every module folder, there is db/ folder where database structure stored. The folder usually contains mysql.php, mysql.sql, etc. for different database.

It's mean that you have to create different files for each database systems. If there are more database you want your module to be compatible with, you have to create more files. XMLDB is intended to solve this problem. Switching to XMLDB is very easy, save your time and effort by creating just 1 file.

Getting Started

XMLDB file in module is stored in db/ folder, named install.xml. You can use a built-in XMLDB editor to create or edit any install.xml files. If you're using MySQL as your default database schemes. XMLDB editor's powerful tools allowing retrofit MySQL table to XMLDB format.

XMLDB editor is located in administration block, go to Miscellaneous > XMLDB editor. Find your module name. You won't be able to click on Create link and also can't edit your module (If Create link is clickable you can skip this step). Since you must make your module folder has write permission first (And if you haven't created db/ folder in your module folder yet, create it now). In Linux operating system, chmod your /db folder to 777 solves this. Now you're ready to create your module's XMLDB files.

Note that XMLDB editor is not a tool for creating your module (It can help you about database). It is a tool to manage XMLDB database file (think about phpmyadmin manages SQL database). You can create tables/fields/keys/indexes or export your exist MySQL tables to XMLDB.

Another XMLDB's advantage is you can create table's comment as you want. To describe it to other developer.

XMLDB editor is really easy to work with. We strongly recommend you to play with it for a while.

More information about XMLDB editor : [1], XMLDB Structure : [2].

Create install.xml

If you never create install.xml before (your db/ doesn't have install.xml), click Create first. install.xml will store your database info for this module.

Start editing

To start edit install.xml, click Load and then Edit. You need to do this every time before editing any XMLDB file. If this is your first time, there is a default table named like your module stored.

Create new table

1. Go to New Table.
2. Enter table name and comment, click change.

Add field in table

1. Click Edit on your desired table.
2. Click New Field, You can now edit field information like name, comment, type, length, etc. See [3] for XMLDB column type comparing with other database system.
3. When you're done, click Change.

Retrofit MySQL table to XMLDB

XMLDB editor can retrofit MySQL table to XMLDB. In other word, it can create XMLDB table from existing SQL. This is useful if your module database already using MySQL. First, your module has to be installed. Then follow these steps:

1. Click New Table from MySQL
2. In Create Table box, choose your table from MySQL database. In After Table choose where would you like to add this table to (It doesn't matter, just for arrangement). Click Create.
3. Do it again untill every table added, you are done !

Note : Table name must contains only lowercase character, number, underscore and length must not exceed 28 characters. More info [4]

See Also

XMLDB_introduction

XMLDB defining an XML structure

XMLDB_column_types

XMLDB editor