i have table have a lot of Names like this
MrMiroBear
MrMiroBear
BigBear
MrMiroBear
BigBear
MrMiroBear
MrMiroBear
BigBear
MrMiroBear
MrMiroBear
BigBear
MrMiroBear
BigBear
BigBear
MrMiroBear
BigBear
BigBear
MrMiroBear
BigBear
select Top 1 Count(*) as TopName From _Client group by ClientName
If your query works, you are not using MySQL.
The answer to your question would then be:
select Top 1 ClientName
From _Client
group by ClientName
order by count(*) desc;
In other words, you have to select the field that you want.
Note: There could be ties. If you want all top client names:
select Top (1) With Ties ClientName
From _Client
group by ClientName
order by count(*) desc;