rails小技巧之分组查询统计并去重

分组查询并统计

SpecialGroup.group(:special_type).count

select special_type,count(*) from special_groups group by special_type

SpecialGroup.group(:special_type).count(:sno)

select special_type,count(sno) from special_groups group by special_type

SpecialGroup.group(:special_type).count("distinct sno")

select special_type,count(distinct sno) from special_groups group by special_type