The count-and-say sequence is the sequence of integers with the first five terms as following: 1. 12. 113. 214. 12115. 111221 1 is read off as “one 1” or 11. 11 is read off
group by 分组 --每个工作的人数select count(job) from emp group by job;--有多少工作select count(coutn(job)) from emp group by job;--每个工作的最高工资select max(sal) from emp group by job;--每个工作的最低工资select min(sal