我们要做一张报表表格，从mysql里取出数据，然后按等级分组，如何实现呢？

MySQL 示例 SQL:

SELECT

ftime,

sum(cost) as cost,

count(advertiser_id) as aduser_num,

sum(pv) as pv,

sum(vc) as vc,

CASE

WHEN cost>100000 THEN ‘1’

WHEN cost>50000 and cost<=100000 THEN ‘2’

WHEN cost>10000 and cost<=50000 THEN ‘3’

WHEN cost>5000 and cost<=10000 THEN ‘4’

WHEN cost>1000 and cost<=5000 THEN ‘5’

WHEN cost>100 and cost<=1000 THEN ‘6’

ELSE ‘7’ END as cost_range

from (

SELECT

ftime,

advertiser_id,

sum(real_cash+vir_cash+gift_cash+divide_cash)/100 as cost,

sum(exposure_cnt) as pv,

sum(valid_click_cnt) as vc

from etail_day

where ftime in(20140603) group by ftime,advertiser_id

) as tmp_table

group by

ftime,CASE

WHEN cost>100000 THEN ‘1’

WHEN cost>50000 and cost<=100 THEN ‘2’

WHEN cost>10000 and cost<=50000 THEN ‘3’

WHEN cost>5000 and cost<=10000 THEN ‘4’

WHEN cost>1000 and cost<=5000 THEN ‘5’

WHEN cost>100 and cost<=1000 THEN ‘6’

ELSE ‘7’ END ;

利用SQL对某个表中的数据按照某个范围进行等级划分，并按照划分后的等级 group by。实现思路见上：

(1)将该表的记录取出，如果有函数运算的话，搞个虚拟字段表示

(2)将(1)中的查询结果构建一张临时表，然后弄一个临时表别名：tmp_table

(3)从临时表中取出数据，按范围group by

可能会遇到的问题：

MySQL Error: Every derived table must have its own alias(这句话的意思是说每个派生出来的表都必须有一个自己的别名)，那可能是别名不对，检查下临时表别名

可能会出现null的值，这时候

◦null和任何值都不能比较

◦null只能用is null 或者is not null 来判断，不能用=或者！=来判断