No longer require database name for MySQL to allow cross database selects.

[#1122 state:committed]
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -53,12 +53,7 @@ def self.mysql_connection(config) # :nodoc:
       socket   = config[:socket]
       username = config[:username] ? config[:username].to_s : 'root'
       password = config[:password].to_s
-
-      if config.has_key?(:database)
-        database = config[:database]
-      else
-        raise ArgumentError, "No database specified. Missing argument: database."
-      end
+      database = config[:database]
 
       # Require the MySQL driver and define Mysql::Result.all_hashes
       unless defined? Mysql

activerecord/test/cases/adapter_test.rb

@@ -63,6 +63,18 @@ def test_collation
     def test_show_nonexistent_variable_returns_nil
       assert_nil @connection.show_variable('foo_bar_baz')
     end
+
+    def test_not_specifying_database_name_for_cross_database_selects
+      assert_nothing_raised do
+        ActiveRecord::Base.establish_connection({
+          :adapter  => 'mysql',
+          :username => 'rails'
+        })
+        ActiveRecord::Base.connection.execute "SELECT activerecord_unittest.pirates.*, activerecord_unittest2.courses.* FROM activerecord_unittest.pirates, activerecord_unittest2.courses"
+      end
+
+      ActiveRecord::Base.establish_connection 'arunit'
+    end
   end
 
   if current_adapter?(:PostgreSQLAdapter)