--> 测试数据：[test]
if object_id('[test]') is not null drop table [test]
create table [test]([id] int,[ch] varchar(7))
insert [test]
select 1,'wwk-222' union all
select 2,'wwk-222' union all
select 3,'wwk-086' union all
select 4,'wwk-076' union all
select 5,'wwk-089' union all
select 6,'wwk-079'

select COUNT(distinct [ch]) as [ch] from test
/*
ch
------
5
*/

--去掉重复使用distinct

------解决方案--------------------
SQL code

--> 测试数据：[test]
if object_id('[test]') is not null drop table [test]
create table [test]([id] int,[ch] varchar(7))
insert [test]
select 1,'wwk-222' union all
select 2,'wwk-222' union all
select 3,'wwk-086' union all
select 4,'wwk-076' union all
select 5,'wwk-089' union all
select 6,'wwk-079'

select * from test a
where a.id=(select MIN(b.id) from test b where a.ch=b.ch)
order by id 
--相同的ch取最大id的时候把min改成max
/*
id    ch
-------------------
1    wwk-222
3    wwk-086
4    wwk-076
5    wwk-089
6    wwk-079
*/