SQL case when

selectbuyer_name,
(
case 
    when buyer_id = '1'
    then '东'
    when buyer_id = '2'
    then '南'
    when buyer_id = '3'
    then '西'
    when buyer_id = '4'
    then '北'
else
    '中'
end
--简单写法
--case buyer_id
-- when '1' then '东'
--  when '2' then '南'
-- when '3' then '西'
-- when '4' then '北'
--else
-- '中'
--end
)asPosition
from dbo.t_join_buyers

create tablet_case_when
(
    zd varchar(20) 
)

insert into t_case_when values ('A001')
insert into t_case_when values ('B001')
insert into t_case_when values ('B002')
insert into t_case_when values ('B003')
insert into t_case_when values ('B004')
insert into t_case_when values ('C001')
insert into t_case_when values ('C002')
insert into t_case_when values ('D001')
insert into t_case_when values ('D002')

select(
case
    when zd like 'A%' then 'A'
    when zd like 'B%' then 'B'
    when zd like 'C%' then 'C'
    when zd like 'D%' then 'D'
else
    'F'
end)
as 开头,count(zd) as数量
fromdbo.t_case_when
group by(
case
    when zd like 'A%' then 'A'
    when zd like 'B%' then 'B'
    when zd like 'C%' then 'C'
    when zd like 'D%' then 'D'
else
    'F'
end)