别名不能用在查询条件里吧。
select username+'-'+userpwd as zd from user where username+'-'+userpwd='admin-1111'
zd 不能在where条件中使用
select username+'-'+userpwd as zd
from user
where username='admin'
and userpwd ='1111'
select username+'-'+userpwd as zd from [user] where username+'-'+userpwd='admin-1111'
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