How do I get Drupal to use table prefixes so I can install multiple drupal installations in the same database schema?
In the settings.php file, a normal setup might look like

$databases['default']['default'] = array(
  'driver' =&gt; 'mysql',
  'database' =&gt; 'databasename',
  'username' =&gt; 'username',
  'password' =&gt; 'password',
  'host' =&gt; 'localhost',
  'collation' =&gt; 'utf8_general_ci',
);


The only difference is that you add a 'prefix', like this:

$databases['default']['default'] = array(
  'driver' =&gt; 'mysql',
  'database' =&gt; 'databasename',
  'username' =&gt; 'username',
  'password' =&gt; 'password',
  'host' =&gt; 'localhost',
  'prefix' =&gt; 'site1_',
  'collation' =&gt; 'utf8_general_ci',
);


Make the prefix different in each settings.php site, and you can have as many sites as you want within the same database.