问题：将全名转换为大写首字母缩写。考虑下面的名字：
Stewie Griffin
要返回如下结果：
S.G.
解决方案：
select
case when cnt=2 then
trim(trailing '.' from
concat_ws('.',
substr(substring_index(name,' ',1),1,1),
substr(name,
length(substring_index(name,' ',1))+2,1),
substr(substring_index(name,' ',-1),1,1),'.'))
else
trim(trailing '.' from
concat_ws('.',
substr(substring_index(name,' ',1),1,1),
substr(substring_index(name,' ',-1),1,1)
))
end as initials
from (
select name,length(name)-length(replace(name,' ','')) as cnt
from (
select replace('Stewie Grifin','.','') as name from t1
)y
)x;