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create table tb
(
pk nvarchar(20) primary key ,
check(substring(pk,1,1) IN('A','B','C','D'))
)
create table tb
(
pk nvarchar(20) primary key ,
check(isnumeric(substring(pk,1,1))=0)
)
insert into tb select 'B111'--正确
insert into tb select '111'--错误