mysql count distinct 加条件

mysql count distinct如何加条件？比如有数据表swimTable：

name swimLocation
张三 A

李四 A

李四 B

张三 A

我想统计游泳馆A有多少人过去？不能使用where，想使用如下语句，但是报错了：
select count(if(swimLocation='A')，distinct name,false) from swimTable；

select sum(distinct name) from swimTable group by swimLocation having swimLocation='A'

select count(distinct name) from swimTable group by swimLocation having swimLocation='A'不好意思上面写错函数了，试一下这个行不

select swimLocation,count(distinct name) from swimTable group by swimLocation

select swimLocation,count(1) from swimTable group by swimLocation

这样会得到 如下数据
A 3
B 1
你循环下数据就可以拿到你想要的数据

可以使用count(distinct case where 条件 then 字段 end)，具体参见：https://stackoverflow.com/questions/19672001/mysql-distinct-count-if-conditions-unique