select
id,
case username
when 'zhangsan' then '张三'
when 'lisi' then '李四'
when 'wangwu' then '王五'
else '未知'
end
as username,
[password]
from student
select
id,
case username
when 'zhangsan' then '张三'
when 'lisi' then '李四'
when 'wangwu' then '王五'
else '未知'
end
as username,
[password]
from student