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select abs(-32);

select floor(1.83);

select floor(-1.83);

select ceiling(1.23);

select ceiling(-1.23);

select round(1.58);

select round(1.58,1);

-- 练习：查询各部门员工人数占比（四舍五入并保留两位小数）

select

deptno,

count(*) as 各部门员工人数,

round(count(*)/(select count(*) from emp),2) as 人数占比

from emp

group by deptno;