Oracle常用查询操作

--整表查询

例子0：desc  查看表结构；

describe s_emp;

desc s_dept;

例子1：查询当前Schema中有多少个表？

select table_name from tabs; 

select table_name from user_tables;

例子2：查询s_emp前三个列的内容?

select id, first_name, last_name  from s_emp;

例子3：显示所有部门的内容？

select * from s_dept;

例子4：显示每位员工的全名？

select id, first_name||’-’||last_name from s_emp;

例子5：员工全名 is in department 部门编号？

select id, first_name||’-’||last_name ||’ is in department ’||dept_id

from s_emp;

例子6：列出每个员工的年薪？

select  id ,first_name, salary*12 from s_emp;

例子7：列出每个员工的一年的总收入？

select id, first_name,

salary*12*(1+NVL(COMMISSION_PCT,0)/100) "total salary"

from s_emp;

例子8：列出所有部门的种类？

select distinct name from s_dept;

例子9：列出各部门有什么不同的职位？

select distinct dept_id , title from s_emp;

--限定查询

例子10： 列出42部门的员工的id,名字，salary,和部门号？

select id, first_name, dept_id

from s_emp

where dept_id = 42;

例子11： 找出工资高于1200元的员工的年薪？

select id, first_name, salary*12  

from s_emp  

where salary > 1200;

例子12： 找出年薪高于12000元的员工？

select id, first_name, salary*12 from s_emp

where salary*12 > 12000;

--- where salary > 1000;

例子13： 找出42部门年薪高于12000元的员工？

select id, first_name, salary*12

from s_emp

where salary > 1000 and dept_id = 42;

例子14： 找出‘Carmen’每个月的工资？

select id, first_name

from s_emp

where first_name=’Carmen’;

例子15： 把所有职位为‘Stock Clerk’的员工列出？

select id, first_name, title

from s_emp

where title=’Stack Clerk’;

例子16： 找出工资在1500-2000之间的员工？

select id,first_name,salary

from s_emp

where salary >= 1500 and salary = 1000 and dept_id=44or dept_id=42;

select *  from s_emp

where salary >= 1000 and (dept_id=44or dept_id=42);

select first_name,dept_id  from s_emp

where dept_id in(42,43)and salary >= 1000;

select first_name,dept_id  from s_emp

where dept_id = any(42,43)and salary >= 1000;

例子24： 按工资降序显示员工的信息？

select id, first_name, salary

from s_emp

order by salary desc;

例子25： 按提成升序显示员工的信息？

select id, first_name, commission_pct

from s_emp

order by 3 asc;

例子26： 先工资降序，再按提成升序显示员工？

select id, first_name, salary, commission_pct

from s_emp

order by salary desc, commission_pct asc;

例子27： 按年薪降序显示员工？

select id, first_name, salary

from s_emp

order by salary*12 desc;

--Oracle函数

【单值函数】

--字符函数

例子28： 当不知道‘Carmen’在数据库是大小写的时，找出‘Carmen’的工资？

select first_name, salary

from s_emp

where lower(first_name)='carmen';

例子29：列出每个员工名字（last_name）的最后两个字符？

select  first_name, length(first_name),

substr(first_name, length(first_name)-1,2)

from s_emp;

select first_name, substr(first_name, -2,2)  from s_emp;

--数值函数

例子30：

ROUND (45.923, 2)45.92

ROUND (45.923, 0)46

ROUND (45.923, -1)50

TRUNC (45.923, 2)    45.92

TRUNC (45.923)    45

TRUNC (45.923, -1)40

--日期函数

alter session set nls_date_format='yyyy mm dd hh24:mi:ss';

例子31： 查出下一天、下一分钟、下一秒的时间

select sysdate as now,

sysdate+1/24 as next_hour,

sysdate+1/(24*60) as next_minute,

sysdate+1/(24*60*60) as next_second

from dual;

例子32：求某天是星期几

select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day') from dual; 星期一

例子33：找出今年的天数

select  add_months(trunc(sysdate,'year'), 12) - trunc(sysdate,'year')

from dual

例子34：今天是一年的第几天

select TO_CHAR(SYSDATE,'DDD'),sysdate  from dual

例子35：闰年的处理方法

to_char( last_day( to_date('02' || &year,'mmyyyy') ), 'dd' )

例子36：按照'yyyy mm dd hh24:mi:ss'的格式，输出42部门员工的入职时间？

select id, first_name, to_char(start_date, 'yyyy-mm-dd hh24:mi:ss')

from s_emp

where dept_id = 42;

例子37：列出5月份入职的员工？

select first_name, to_char(start_date,'dd-mon-yyyy hh24:mi:ss')

from s_emp

where to_char(start_date,'mm') = '05';

--where to_char(start_date,'fmmm') = '5';

--where to_char(start_date,'fmmm') = 5;

-- where to_char(start_date,'MONTH') = '5';

-- where to_char(start_date, 'MONTH') ='MAY;

select  first_name,

to_char(start_date,'dd-mon-yyyy hh24:mi:ss') as startt,

to_char(start_date,'MONTH') as datet,

length(to_char(start_date,'fmMONTH')) as lengtht

from s_emp

where rtrim(to_char(start_date,'MONTH')) = 'MAY';

例子38：求出下个月的1号？

select last_day(sysdate)+1 from dual;

select round(last_day(sysdate),'MONTH') from dual;

select add_months(trunc(sysdate,'MONTH'),1) from dual;

select trunc(add_months(sysdate,1),'MONTH') from dual;

例子39：找出90年上半年入职的员工信息？

select first_name, start_date

from s_emp

--where round(start_date,’YEAR’) = ‘2010-01-01’; --error

--where round(start_date,'year') = '1-1月-90'

where  to_char(start_date,'mm') 15;

--转换函数

例子41：

to_char();

to_number();

to_date();

--组函数

例子42：列出提成的平均值？

select avg(commission_pct)

from s_emp;

例子43：列出提成的最大值？

select max(commission_pct)

from s_emp;

例子44：求出有提成的员工个数？

select count(commission_pct)

from s_emp;

count():组函数对非空值进行统计。

select count(*)

from s_emp

where commission_pct is not null;

例子45：求出42部门的平均工资？（只显示平均工资）

select avg(salary)

from s_emp

where dept_id = 42;

--group by

例子46：求出42部门的平均工资？（显示部门号、平均工资）

select max(dept_id), avg(salary)

from s_emp

where dept_id = 42;

select dept_id, avg(salary)

from s_emp

where dept_id = 42

group by dept_id;

例子47：求出各部门的平均工资？

select dept_id,avg(salary)

from s_emp

group by dept_id;

select dept_id ,         sum(salary)||'/'||count(*)||'='||sum(salary)/count(*) as avg

from s_emp

group by dept_id

order by dept_id;

例子48：求出各职位的平均工资？(要求：列出职位名称和平均工资)

select title, avg(salary)

from s_emp

group by title;

例子49：求出各部门不同职位的平均工资？

select dept_id,title, avg(salary)

from s_emp

group by dept_id, title

order by dept_id;

--having

例子50：求出平均工资高于2000的员工？ 

select first_name, max(salary)

from s_emp

--where avg(salary) > 2000;

group by first_name

having avg(salary) > 2000;

求出部门平均工资高于2000的员工信息？ 

select id, first_name,dept_id

from s_emp

where  dept_id in ( select dept_id

               from s_emp

               group by dept_id

               having avg(salary) >= 2000

              );

测试：

select id, first_name,dept_id

from s_emp

where  dept_id in (

               select dept_id,avg(salary)

               from s_emp

               where salary >= 1000

               group by dept_id

               having avg(salary) >= 1500

               order by dept_id asc

              );

例子51：求出各部门的平均工资？ （要求显示：区域名称、部门编号、部门名称、平均工资）？？？

select d.id, max(r.name)||'_'||min(d.name) as dept, avg(salary)

from s_emp e, s_dept d, s_region r

where e.dept_id = d.id

and d.region_id = r.id

group by d.id

order by d.id;