group by case when用法

group by case when 用法

select的字段要和group by的一樣，並且group by不能用別名

select   case when left(tagName,4)='http' then 'http'
when left(tagName,3) = '數據庫' then '數據庫'
else 0
end as tagName,count(1)
 from IP_gene_info
group by (case when left(tagName,4)='http' then 'http'
when left(tagName,3) = '數據庫' then '數據庫'
else 0
end )