1、distinct
select count(distinct CName) from teble
select count(CName) from (select distinct CName from Course) as temp
SELECT DISTINCT text_zhcn FROM dms_menuconfig -- 去重查询表中数据
select DISTINCT(user_id) from user_info where children_merchant_id='kuaiditong';
2、group by
select count(1) from Course group by CName
Documentation: mysql query table data de-duplication .note
link: http://note.youdao.com/noteshare?id=581440d92396bab4de6568d1a69baa58&sub=9B8DAB091CC5490BA5F8FA29557CCD67