The manifest file in this example is very similar to that of normal components. Important contents for this example include:
Note the inclusion of the SQL folder in the administration files section. This tells Joomla to copy the contents of this folder to the web site during install or update. The SQL folder contains individual SQL files for each incremental update.
<administration> <files folder="admin"> <folder>sql</folder> </files> </administration>
This is the name of the component. The 'getParam($key)' method in the script.php file uses this value to identify the correct row in the extensions table. The manifest_cache field in the extensions table has the version string for the currently installed component.
Joomla stores this value in the manifest_cache field of the extensions table. This table is where the custom code in the script.php file reads the version string of the currently installed component, to compare to the version string of the update. The custom component code uses this comparison to abort an update. Joomla also compares this string to the SQL update file names, to determine which SQL commands to execute.
This defines the directory that contains SQL files for component incremental database updates. You may choose to put the SQL files somewhere else in your component release, but make sure their location is documented here.
<update> <schemas> <schemapath type="mysql">sql/updates</schemapath> </schemas> </update>