Disabling referential integrity examples with ruby (and probably rails too)

db_examples_on_activerecord.rb

## ORACLE
def disable_referential_integrity(&block) #:nodoc:
        sql_constraints = <<-SQL
        SELECT constraint_name, owner, table_name
          FROM user_constraints
          WHERE constraint_type = 'R'
          AND status = 'ENABLED'
        SQL
        old_constraints = select_all(sql_constraints)
        begin
          old_constraints.each do |constraint|
            execute "ALTER TABLE #{constraint["table_name"]} DISABLE CONSTRAINT #{constraint["constraint_name"]}"
          end
          yield
        ensure
          old_constraints.each do |constraint|
            execute "ALTER TABLE #{constraint["table_name"]} ENABLE CONSTRAINT #{constraint["constraint_name"]}"
          end
        end
      end

## SQLSERVER
def disable_referential_integrity
        do_execute "EXEC sp_MSforeachtable 'ALTER TABLE ? NOCHECK CONSTRAINT ALL'"
        yield
      ensure
        do_execute "EXEC sp_MSforeachtable 'ALTER TABLE ? CHECK CONSTRAINT ALL'"
      end

## MYSQL
def disable_referential_integrity #:nodoc:
        old = select_value("SELECT @@FOREIGN_KEY_CHECKS")

        begin
          update("SET FOREIGN_KEY_CHECKS = 0")
          yield
        ensure
          update("SET FOREIGN_KEY_CHECKS = #{old}")
        end
      end

## POSTGRES
def disable_referential_integrity #:nodoc:
        if supports_disable_referential_integrity? then
          execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} DISABLE TRIGGER ALL" }.join(";"))
        end
        yield
      ensure
        if supports_disable_referential_integrity? then
          execute(tables.collect { |name| "ALTER TABLE #{quote_table_name(name)} ENABLE TRIGGER ALL" }.join(";"))
        end
      end

More informations about how database_cleaner gem uses thoses methods,
https://github.com/bmabey/database_cleaner/blob/master/lib/database_cleaner/active_record/truncation.rb#L248