How to create a table without uninstalling and reinstalling the module?

Question

I have a module and an installation file that is used to create a table.

According to my requirement, I need to add an another table in the same install file. I know that by using hook_schema() we can create n number of tables.
But we need to uninstall and reinstall again to create the tables. If I use this, my existing data will be lost, so I am not supposed to do this.

Is there any way to create a table without uninstalling and reinstalling the module?

Answer 1

This link answered my question: Updating tables: hook_update_N() functions.

For example:

In Drupal 7:

<?php
/**
 * Create new database table {mytable2}.
 */
function mymodule_update_7101() {
  $schema['mytable2'] = array(
     // table definition array goes here
  );
  db_create_table('mytable2', $schema['mytable2']);
}
?>

and in Drupal 6:

<?php
/**
 * Create new database table {mytable2}.
 */
function mymodule_update_6101() {
  $schema['mytable2'] = array(
     // table definition array goes here
  );
  $ret = array();
  db_create_table($ret, 'mytable2', $schema['mytable2']);
  return $ret;
}
?>

Answer 2

hook_install() is called only when the module is first installed; after that, hook_install() will be called only if you first uninstall the module.

When you are updating a module, you need to implement hook_update_N(), which runs all times the module is updated. At the same time, the implementation of hook_schema() needs to be updated to include all the schema used from the module, for who installs the module for the first time.