lib/sequel/migration_builder.rb
def alter_table_statement(table_name, operations)
      add_line "alter_table #{table_name.inspect} do"
      indent do
        operations.compact.each {|op| add_line op }
      end
      add_line "end"
    end
def alter_table_statement(table_name, operations)
      add_line "alter_table #{table_name.inspect} do"
      indent do
        operations.compact.each {|op| add_line op }
      end
      add_line "end"
    end
Generates an individual alter table statement.