What are the different attribute data types?
select distinct attribute_data_type from attribute_definitions
How many attributes are of each type?
select attribute_data_type, count(*) from attribute_definitions group by attribute_data_type
What datatypes have more than 1?
select attribute_data_type from attribute_definitions group by attribute_data_type having count(*) > 1
How about more than 3?
select attribute_data_type from attribute_definitions group by attribute_data_type having count(*) > 3