result = ActiveRecord::Base.connection.execute("select 'ABC'")

activerecord (2.3.9)
mysql (2.8.1)

result.first[0]
# or
result.first['ABC']

result.first[0]
# or
result.first['ABC']

result.first[0]
# or
result.first['ABC']

result = ActiveRecord::Base.connection.select_value("select 'ABC'")

ActiveRecord::Base.connection.select_all("select 'ABC'")