怎样获取数据库中某个表中某列中指定字符的数量

select length(sname)-length(replace(sname,'r','')) from a

declare @tmp varchar(2000)
declare @m int
declare @i int
declare @s varchar(1)

set @tmp='rerewerewrew'
set @s='r'
set @i=0
set @m=0
while charindex(@s ,@tmp)>0
begin
set @m=charindex(@s,@tmp)
set @tmp=substring(@tmp,@m+1,len(@tmp))
set @i=@i+1
end
select @i

select len(sname)-len(replace(sname,'r','')) from a

select count(*) from a where sanme = 'rerewerewrew'