employee表中lastname列保存顾客姓,firstname列保存顾客的名,现在,需要查询顾客的姓名的组合,例如,lastname列中的”张“,同一行firstname列中的”“,查询结果应该返回”张“,则正确的查询语句应该是( )
A.
select lastname,firstname from employee
B.
select * from employee order by lastname,firstname
C.
select lastname+firstname from employee
D.
select lastname and firstname from employee