目錄
sql語句學習
/*sql語句學習*/
/*
SELECT [DISTINCT] {*, column alias,..}
FROM table alias
Where 條件表達式
*/
--查詢EMP表中部門標號是10的員工
select empno, ename, job from emp where deptno = 10;
--distinct 去除重複數據
select distinct deptno from emp;
--去重也可以針對多個字段,多個字段值只要有一個不匹配就算是不同的記錄
select distinct deptno,sal from emp;
--查詢過程中可以給列添加別名,也可以給表添加別名
select e.empno 僱員編號,e.ename 僱員名稱, e.job 僱員工作 from emp e where e.deptno=10;
--給列起別名,可以加as,也可以不加,看心情
select e.empno as 僱員編號,e.ename as 僱員名稱, e.job as 僱員工作 from emp e where e.deptno=10;
--給列起別名,如果別名中包含空格,那麼需要將別名用""包含起來
select e.empno as "僱員 編號",e.ename as "僱員 名稱", e.job as "僱員 工作" from emp e where e.deptno=10;
--查詢表中的所有字段,可以使用*,但是項目中千萬不要隨便使用*,容易被打死
select * from emp;
/*
=,!=,<>,<,>,<=,>=,any,some,all
is null,is not null
between x and y
in(list),not in(list)
exists(sub-query)
like _ ,%,escape ‘\‘ _\% escape ‘\’
*/
-- =
select * from emp where deptno = 20;
-- !=
select * from emp where deptno != 20;
-- <> 不等於
select * from emp where deptno <> 20;
-- <
select sal from emp where sal < 1500;
-- >
select sal from emp where sal < 1500;
-- <=
select sal from emp where sal <= 1500;
-- >=
select sal from emp where sal >= 1500;
-- any,取其中任意一個
select sal from emp where sal > any(1000,1500,3000);
--some,some跟any是同一個效果,只要大於其中某一個值都會成立
select sal from emp where sal > some(1000,1500,3000);
--all,大於所有的值纔會成立
select sal from emp where sal > all(1000,1500,3000);
-- is null,在sql語法中,null表示一個特殊的含義,null != null,不能使用=或!=判斷,需要使用is或is not
select * from emp where comm is null;
-- is not null
select * from emp where comm is not null;
select * from emp where null is null;
-- between x and y ,包含x和y的值
select * from emp where sal between 1500 and 3000;
select * from emp where sal >= 1500 and sal<3000;
--需要進行某些值的等值判斷的時候可以使用in和not in
--in(list)
select * from emp where deptno in(10,20);
--可以用and和or這樣的關鍵字,and相當於與操作,or相當於或操作
--and和or可能出現在同一個sql語句中,此時需要注意and和or的優先級,and的優先級高於or,所以一定要將or的相關操作用()括起來提高優先級
select * from emp where deptno = 10 or deptno = 20;
--not in(list)
select * from emp where deptno not in(10,20);
select * from emp where deptno != 10 and deptno != 20;
/*exists(sub-query) ,當exists中的子查詢語句能查到對應結果的時候,意味着條件滿足
相當於雙層for循環
查詢部門編號爲10和20的員工,要求使用exists實現*/
select * from emp where deptno = 10 or deptno = 20;
--通過外層循環來規範內層循環
select *
from emp e
where exists (select deptno
from dept d
where (d.deptno = 10 or d.deptno = 20)
and e.deptno = d.deptno);
/*
模糊查詢:
like _ ,%,escape ‘\‘ _\% escape ‘\’
在like語句中,需要使用佔位符或者通配符
_,代表某個字符或者數字僅出現一次
%,任意字符出現任意次數
escape,使用轉義字符,可以自己規定轉義字符
使用like的時候要慎重,因爲like的效率比較低;
使用like可以參考使用索引,但是要求不能以%開頭
涉及到大文本的檢索的時候,可以使用某些框架,如luence,solr,elastic search
*/
--查詢名字以s開頭的用戶
select * from emp where ename like('S%')
--查詢名字以s開頭且倒數第二個字符爲T的用戶
select * from emp where ename like('S%T_');
--查詢名字中帶%的用戶
select * from emp where ename like('%\%%') escape('\');
select * from emp where ename like('%a%%') escape('a');
/*order by進行排序操作
默認情況下完成的是升序的操作,
asc:是默認的排序方式,表示升序
desc:降序的排序方式
排序是按照自然順序進行排序的。
如果是數值,那麼按照從大到小;
如果是字符串,那麼按照字典序排序。
進行排序的時候,可以指定多個字段,而且多個字段可以使用不同的排序方式
每次在執行order by的時候相當於是做了全排序,思考全排序的效率
全排序會比較耗費系統的資源,因此選擇在業務不太繁忙的時候進行
*/
select * from emp order by sal;
select * from emp order by sal desc;
select * from emp order by ename;
select * from emp order by sal desc, ename asc;
--使用計算字段
--字符串連接符
select 'my name is ' || ename from emp;
select concat('my name is ',ename) from emp;
--計算所有員工的年薪
--這種方式計算不出年薪,因爲任何值+null都還是爲null
select ename,(e.sal+e.comm)*12 from emp e;
--null是比較特殊的存在,null做任何運算都還是爲null,因此要將null進行轉化
--引入函數nvl:nvl(arg1, arg2),如果arg1=null,那麼返回arg2;如果不等於空,則返回原來的值
select ename, (e.sal + nvl(e.comm, 0)) * 12 from emp e;
--dual是oracle數據庫中的一張虛擬表,沒有實際的數據,可以用來做測試
select 100 + null from dual;
--A集合
select * from emp where deptno = 30;
--B集合
select * from emp where sal > 1000;
--並集,將兩個集合中的所有數據都進行顯示,但是不包含重複的數據
select * from emp where deptno = 30
union
select * from emp where sal > 1000;
--全集,將兩個集合的數據全部顯示,不會完成去重的操作
select * from emp where deptno = 30
union all
select * from emp where sal > 1000;
--交集,兩個集合中的交叉的數據集,只顯示一次
select * from emp where deptno = 30
intersect
select * from emp where sal > 1000;
--差集,包含在A集合而不包含在B集合中的數據,跟A和B的集合順序相關
select * from emp where deptno = 30
minus
select * from emp where sal > 1000;
練習
數據庫中有如下4個表:
其中:
BONUS表:
DEPT表:
EMP表:
SALGRADE表:
根據這四張表進入如下的數據庫操作。sql中"--"用於註釋。
--練習
--1、查詢部門編號爲10的員工信息
select * from emp where deptno = 10;
--2、查詢年薪大於3萬的人員的姓名與部門編號
select ename,deptno from emp where sal*12 > 30000;
--3、查詢佣金爲null的人員姓名與工資
select ename,sal from emp where comm is null;
--4、查詢工資大於1500且and含有佣金的人員的姓名
select ename from emp where sal > 1500 and comm is not null;
--5、查詢工資大於1500或or含有佣金的人員姓名
select ename from emp where sal > 1500 or comm is not null;
--6、查詢姓名裏面含有S的員工信息 工資 名稱
select sal,ename from emp where ename like('%S%');
--7、求姓名以J開頭,第二個字符O的員工姓名與工資
select ename,sal from emp where ename like('JO%');
--8、求包含%的僱員姓名
select ename from emp where ename like('%\%%') escape('\');
--9、使用in查詢部門名稱爲SALES和RESEARCH的僱員姓名、工資、部門編號
select ename, sal, deptno
from emp
where deptno in
(select deptno from dept where dname in ('SALES', 'RESEARCH'));
--10、使用exists查詢部門名稱爲SALES和RESEARCH的僱員姓名、工資、部門編號
select ename, sal, deptno
from emp e
where exists (select deptno
from dept d
where dname in ('SALES', 'RESEARCH')
and e.deptno = d.deptno);
--(1)查詢20號部門的所有員工信息
select * from emp where deptno = 20;
--(2) 查詢所有工種爲CLERK的員工的工號、員工名和部門編號
select empno,ename,deptno from emp where job = 'CLERK';
--(3) 查詢獎金(COMM)高於工資(SAL)的員工信息
select * from emp where comm > sal;
--(4) 查詢獎金高於工資的20%的員工信息
select * from emp where comm > (sal*0.2);
--(5) 查詢10號部門中工種爲MANAGER或20號部門中工種爲CLERK的員工的信息
select * from emp where (deptno = 10 and job = 'MANAGER') or (deptno = 20 and job = 'CLERK');
--(6) 查詢所有工種不是MANAGER和CLERK,且工資大於或等於2000的員工的詳細信息
select * from emp where job not in('MANAGER','CLERK') and sal >= 2000;
--(7) 查詢有獎金的員工的不同工種
select distinct job from emp where comm is not null;
--(8) 查詢所有員工工資和獎金的和 !!!!!!
select ename,(sal+nvl(comm,0)) salcomm from emp;
--(9) 查詢沒有獎金或獎金低於100的員工信息
select * from emp where (comm is null or comm < 100);
--(10) 查詢各月倒數第2天入職的員工信息 !!!!!!!
select * from emp where hiredate in (select (last_day(hiredate)-1) from emp);
--(11) 查詢員工工齡大於或等於10年的員工信息 !!!!!!!
select * from emp where (sysdate - hiredate)/365 >= 10;
-- (12) 查詢員工信息,要求以首字母大寫的方式顯示所有員工的姓名 (數據庫中有很多內置函數)
select upper(substr(ename,1,1)) || lower(substr(ename,2,length(ename)-1)) from emp;
--(13) 查詢員工名正好爲6個字符的員工的信息
select * from emp where length(ename) = 6;
--(14) 查詢員工名字中不包含字母“S”員工
select * from emp where ename not like('%S%');
select * from emp where ename not in (select ename from emp where ename like('%S%'));
--(15) 查詢員工姓名的第2個字母爲“M”的員工信息。
select * from emp where ename like('_M%');
--(16) 查詢所有員工姓名的前3個字符。
select substr(ename,1,3) from emp;
--(17) 查詢所有員工的姓名,如果包含字母“s”,則用“S”替換
select replace(ename,'s','S') from emp;
--(18) 查詢員工的姓名和入職日期,並按入職日期從先到後進行排列
select ename,hiredate from emp order by hiredate asc;
--(19) 顯示所有的姓名、工種、工資和獎金,按工種降序排列,若工種相同則按工資升序排列
select ename,job,sal,comm from emp order by job desc, sal asc;
--(20) 顯示所有員工的姓名、入職的年份和月份,若入職日期所在的月份排序,若月份相同則按入職的年份排序
select ename, to_char(hiredate, 'yyyy') || '-' || to_char(hiredate, 'mm')
from emp
order by to_char(hiredate, 'mm'), to_char(hiredate, 'yyyy');
--(21) 查詢在2月份入職的所有員工信息
select * from emp where to_char(hiredate,'mm')=2;
--(22) 查詢所有員工入職以來的工作期限,用“**年**月**日”的形式表示
select ename,
floor((sysdate - hiredate) / 365) || '年' ||
floor(mod((sysdate - hiredate), 365) / 30) || '月' ||
ceil(mod(mod((sysdate - hiredate), 365), 30)) || '天'
from emp;
--(23) 查詢至少有一個員工的部門信息
select *
from dept
where deptno in (select distinct deptno from emp where mgr is not null);
--(24) 查詢工資比SMITH員工工資高的所有員工信息
select *
from emp
where sal > (select sal from emp where ename like 'SMITH');
--(25) 查詢所有員工的姓名及其直接上級的姓名
select staname, ename supname
from (select ename staname, mgr from emp) t
join emp
on t.mgr = emp.empno;
--(26) 查詢入職日期早於其直接上級領導的所有員工信息。
select *
from emp
where empno in
(select staempno
from (select empno staempno, hiredate stahiredate, mgr from emp) t
join emp
on t.mgr = emp.empno
and stahiredate < hiredate);
--(27) 查詢所有部門及其員工信息,包括那些沒有員工的部門
select *
from dept
left join emp
on emp.deptno = dept.deptno
order by dept.deptno;
--(28) 查詢所有員工及其部門信息,包括那些還不屬於任何部門的員工
select *
from emp
left join dept
on emp.deptno = dept.deptno
order by emp.empno;
--(29) 查詢所有工種爲CLERK的員工的姓名及其部門名稱。
select ename, dname
from emp
join dept
on job like 'CLERK'
and emp.deptno = dept.deptno;
select emp.ename, dept.dname
from emp
join dept
on emp.deptno = dept.deptno
where job = 'CLERK';
--(30) 查詢最低工資大於2500的各種工作
select job
from (select min(sal) min_sal, job from emp group by job)
where min_sal > 2500;
--(31) 查詢最低工資低於2000的部門及其員工信息。
select *
from emp
where deptno in
(select distinct deptno
from (select min(sal) min_sal, deptno from emp group by deptno)
where min_sal < 2000);
--(32) 查詢在SALES部門工作的員工的姓名信息。
select ename
from emp
where deptno in (select deptno from dept where dname = 'SALES');
select ename
from emp
where deptno = (select deptno from dept where dname like 'SALES');
--(33) 查詢工資高於公司平均工資的所有員工信息
select * from emp where sal > (select avg(sal) from emp);
--(34) 查詢與SMITH員工從事相同工作的所有員工信息
select *
from emp
where job in (select job from emp where ename like 'SMITH')
and ename not like 'SMITH';
--(35) 列出工資等於30號部門中某個員工工資的所有員工的姓名和工資
select ename, sal
from emp
where sal = any (select sal from emp where deptno = 30);
--(36) 查詢工資高於30號部門中工作的所有員工的工資的員工姓名和工資
select ename,sal from emp where sal > all(select sal from emp where deptno = 30);
--(37) 查詢每個部門中的員工數量、平均工資和平均工作年限
select dname, empcount, avg_sal, avg_date
from dept
join (select count(*) empcount,
avg(sal) avg_sal,
avg((sysdate - hiredate) / 365) avg_date,
deptno
from emp
group by deptno) t
on dept.deptno = t.deptno;
--(38) 查詢從事同一種工作但不屬於同一部門的員工信息。
select distinct t1.empno, t1.ename, t1.deptno
from emp t1
join emp t2
on t1.job like t2.job
and t1.deptno <> t2.deptno;
--(39) 查詢各個部門的詳細信息以及部門人數、部門平均工資
select dept.*, person_num, avg_sal
from dept,
(select count(*) person_num, avg(sal) avg_sal, deptno
from emp
group by deptno) t
where dept.deptno = t.deptno;
--(40) 查詢各種工作的最低工資
select job, min(sal) from emp group by job;
--(41) 查詢各個部門中的不同工種的最高工資
select max(sal), job, deptno
from emp
group by deptno, job
order by deptno, job;
--(42) 查詢10號部門員工以及領導的信息。
select *
from emp
where empno in (select mgr from emp where deptno = 10);
or deptno = 10;
--(43) 查詢各個部門的人數及平均工資
select deptno, count(*), avg(sal) from emp group by deptno;
--(44) 查詢工資爲某個部門平均工資的員工信息
select * from emp where sal in (select avg(sal) avg_sal from emp group by deptno);
--(45) 查詢工資高於本部門平均工資的員工的信息
select emp.*
from emp
join (select deptno, avg(sal) avg_sal from emp group by deptno) t
on emp.deptno = t.deptno
and sal > avg_sal;
--(46) 查詢工資高於本部門平均工資的員工的信息及其部門的平均工資
select emp.*, avg_sal
from emp
join (select deptno, avg(sal) avg_sal from emp group by deptno) t
on emp.deptno = t.deptno
and sal > avg_sal;
--(47) 查詢工資高於20號部門某個員工工資的員工的信息
select * from emp where sal > any (select sal from emp where deptno = 20);
--(48) 統計各個工種的人數與平均工資
select job, count(*), avg(sal) from emp group by job;
--(49) 統計每個部門中各個工種的人數與平均工資
select deptno, job, count(*), avg(sal)
from emp
group by deptno, job
order by deptno, job;
--(50) 查詢工資、獎金與10 號部門某個員工工資、獎金都相同的員工的信息
select emp.*
from emp
join (select sal, comm from emp where deptno = 10) t
on emp.sal = t.sal
and nvl(emp.comm, 0) = nvl(t.comm, 0)
and emp.deptno != 10;
--(51) 查詢部門人數大於5的部門的員工的信息
select *
from emp
where deptno in
(select deptno from emp group by deptno having count(*) > 5);
--(52) 查詢所有員工工資都大於1000的部門的信息
select *
from dept
where deptno in
(select distinct deptno
from emp
where deptno not in
(select distinct deptno from emp where sal < 1000));
--(53) 查詢所有員工工資都大於1000的部門的信息及其員工信息
select *
from emp
join dept
on dept.deptno in
(select distinct deptno
from emp
where deptno not in
(select distinct deptno from emp where sal < 1000))
and dept.deptno = emp.deptno;
--(54) 查詢所有員工工資都在900~3000之間的部門的信息
select *
from dept
where deptno in (select distinct deptno
from emp
where deptno not in
(select distinct deptno
from emp
where sal not between 900 and 3000));
--(55) 查詢所有工資都在900~3000之間的員工所在部門的員工信息。
select *
from emp
where deptno in (select distinct deptno
from emp
where deptno not in
(select distinct deptno
from emp
where sal not between 900 and 3000));
--(56) 查詢每個員工的領導所在部門的信息
select *
from (select e1.empno, e1.ename, e1.mgr mno, e2.ename mname, e2.deptno
from emp e1
join emp e2
on e1.mgr = e2.empno) t
join dept
on t.deptno = dept.deptno;
--(57) 查詢人數最多的部門信息
select *
from dept
where deptno in
(select deptno
from (select count(*) count, deptno from emp group by deptno)
where count in
(select max(count)
from (select count(*) count, deptno from emp group by deptno)));
--(58) 查詢30號部門中工資排序前3名的員工信息。
select *
from emp
where empno in (select empno
from (select empno, sal
from emp
where deptno = 30
order by sal desc)
where rownum < 4);
--(59) 查詢所有員工中工資排在5~10名之間的員工信息
select *
from emp
where empno in (select empno
from (select empno, rownum num
from (select empno, sal from emp order by sal desc))
where num between 5 and 10);
select empno
from (select empno, sal from emp order by sal desc)
where rownum <= 10
minus
select empno
from (select empno, sal from emp order by sal desc)
where rownum < 5;
--(60) 向emp表中插入一條記錄,員工號爲1357,員工名字爲oracle,工資爲2050元,部門號爲20,入職日期爲2002年5月10日
insert into emp
(empno, ename, sal, deptno, hiredate)
values
(1357,
'oracle',
2050,
20,
to_date('2002年5月10日', 'yyyy"年"mm"月"dd"日"'));
--(61) 向emp表中插入一條記錄,員工名字爲FAN,員工號爲8000,其他信息與SMITH員工的信息相同
insert into emp
select 8000, 'FAN', job, mgr, hiredate, sal, comm, deptno
from emp
where ename = 'SMITH';
--(62) 將各部門員工的工資修改爲該員工所在部門平均工資加1000。
update emp t1
set sal =
(select new_sal
from (select avg(sal) + 1000 new_sal, deptno
from emp
group by deptno) t2
where t1.deptno = t2.deptno);
--1、查詢82年員工
select e.* from emp e where to_char(e.hiredate, 'yy') like '82';
select e.* from emp e where to_char(e.hiredate, 'yyyy') = '1982';
--2、查詢32年工齡的人員
select round(sysdate - e.hiredate) / 365, e.ename, e.hiredate
from emp e
where round((sysdate - e.hiredate) / 365) = 32;
--3、顯示員工僱傭期 6 個月後下一個星期一的日期
select next_day(add_months(e.hiredate, 6), 2) from emp e;
--4、找沒有上級的員工,把mgr的字段信息輸出爲 "boss"
select decode(e.mgr, null, 'boss', '中國好聲音') from emp e;
--5、爲所有人漲工資,標準是:10部門長10%;20部門長15%;30部門長20%其他部門長18%
select decode(e.deptno, 10, e.sal * 1.1, 20, e.sal * 1.15, e.sal * 1.18) 漲工資,
e.deptno,
e.sal
from emp e;
--1、求部門中薪水最高的人
select ename, sal, emp.deptno
from emp
join (select deptno, max(sal) max_sal from emp group by deptno) t
on (emp.deptno = t.deptno and emp.sal = t.max_sal);
select ename, sal, deptno
from emp
where sal in (select max(sal) from emp group by deptno);
--2、求部門平均薪水的等級
select deptno, avg_sal, grade
from (select deptno, avg(sal) avg_sal from emp group by deptno) t
join salgrade
on (t.avg_sal between salgrade.losal and salgrade.hisal);
--3、求部門平均的薪水等級
select deptno, avg(grade) avg_sal_grade
from (select deptno, grade
from emp
join salgrade
on emp.sal between salgrade.losal and salgrade.hisal)
group by deptno;
--4、僱員中有哪些人是經理人
select distinct e2.ename manager
from emp e1
join emp e2
on e1.mgr = e2.empno;
select ename from emp where empno in (select mgr from emp);
--5、不準用組函數,求薪水的最高值
select distinct sal max_sal
from emp
where sal not in
(select e1.sal e1_sal from emp e1 join emp e2 on e1.sal < e2.sal);
select * from (select * from emp order by sal desc) t where rownum < 2;
--6. 求平均薪水最高的部門的部門編號
select deptno, avg_sal
from (select deptno, avg(sal) avg_sal from emp group by deptno)
where avg_sal =
(select max(avg_sal)
from (select avg(sal) avg_sal from emp group by deptno));
--組函數嵌套寫法(對多可以嵌套一次,group by 只對內層函數有效)
select deptno, avg_sal
from (select deptno, avg(sal) avg_sal from emp group by deptno)
where avg_sal = (select max(avg(sal)) from emp group by deptno);
--7、求平均薪水最高的部門的部門名稱
select t1.deptno, dname, avg_sal
from (select deptno, avg(sal) avg_sal from emp group by deptno) t1
join dept
on t1.deptno = dept.deptno
where avg_sal =
(select max(avg_sal)
from (select deptno, avg(sal) avg_sal from emp group by deptno));
select dname
from dept
where deptno =
(select deptno
from (select deptno, avg(sal) avg_sal from emp group by deptno)
where avg_sal = (select max(avg_sal)
from (select deptno, avg(sal) avg_sal
from emp
group by deptno)));
--8、求平均薪水的等級最低的部門的部門名稱
select dname
from dept
join (select deptno, grade
from (select deptno, avg(sal) avg_sal from emp group by deptno) t
join salgrade
on (t.avg_sal between salgrade.losal and salgrade.hisal)) t
on dept.deptno = t.deptno
where t.grade =
(select min(grade)
from (select avg(sal) avg_sal from emp group by deptno) t
join salgrade
on (t.avg_sal between salgrade.losal and salgrade.hisal));
--9、求部門經理人中平均薪水最低的部門名稱
select dname
from (select deptno, avg(sal) avg_sal
from emp
where empno in (select mgr from emp)
group by deptno) t
join dept
on t.deptno = dept.deptno
where avg_sal = (select min(avg_sal)
from (select avg(sal) avg_sal
from emp
where empno in (select mgr from emp)
group by deptno) t);
--10、求比普通員工的最高薪水還要高的經理人名稱(not in)
select ename
from emp
where empno in (select mgr from emp)
and sal > (select max(sal)
from (select e2.sal
from emp e1
right join emp e2
on e1.mgr = e2.empno
where e1.ename is null) t);
select ename
from emp
where empno in (select mgr from emp)
and sal >
(select max(sal)
from emp
where empno not in
(select distinct mgr from emp where mgr is not null));
--NOT IN遇到NULL則返回NULL,必須排除NULL值
--11、求薪水最高的前5名僱員
select empno, ename
from (select * from emp order by sal desc)
where rownum <= 5;
--12、求薪水最高的第6到第10名僱(!important)
select ename, sal
from (select t.*, rownum r from (select * from emp order by sal desc) t)
where r >= 6
and r <= 10;
--13、求最後入職的5名員工
select ename, to_char(hiredate, 'YYYY"年"MM"月"DD"日"') hiredate
from (select t.*, rownum r
from (select * from emp order by hiredate desc) t)
where r <= 5;
select ename, to_char(hiredate, 'YYYY"年"MM"月"DD""') hiredate
from (select t.*, rownum r from (select * from emp order by hiredate) t)
where r > (select count(*) - 5 from emp);