select count(*) from emp;
select count(idcard) from emp;
select avg(age) from emp;
select max(age) from emp;
select min(age) from emp;
select sum(age) from emp where workaddress = "西安";
select count(*) from emp;
select count(idcard) from emp;
select avg(age) from emp;
select max(age) from emp;
select min(age) from emp;
select sum(age) from emp where workaddress = "西安";