create table emp2 ( empno number(4), ename varchar2(10), job varchar2(9), mgr number(4), hiredate date, sal number(7,2), comm number(7,2), deptno number(2) ); ----------------------------------------------------------------------------------------------------------- insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7369, 'SMITH', 'CLERK', 7902, to_date('17-12-1980', 'dd-mm-yyyy'), 800.00, null, 20); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7499, 'ALLEN', 'SALESMAN', 7698, to_date('20-02-1981', 'dd-mm-yyyy'), 1600.00, 300.00, 30); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7521, 'WARD', 'SALESMAN', 7698, to_date('22-02-1981', 'dd-mm-yyyy'), 1250.00, 500.00, 30); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7566, 'JONES', 'MANAGER', 7839, to_date('02-04-1981', 'dd-mm-yyyy'), 2975.00, null, 20); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7654, 'MARTIN', 'SALESMAN', 7698, to_date('28-09-1981', 'dd-mm-yyyy'), 1250.00, 1400.00, 30); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7698, 'BLAKE', 'MANAGER', 7839, to_date('01-05-1981', 'dd-mm-yyyy'), 2850.00, null, 30); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7782, 'CLARK', 'MANAGER', 7839, to_date('09-06-1981', 'dd-mm-yyyy'), 2450.00, null, 10); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7788, 'SCOTT', 'ANALYST', 7566, to_date('19-04-1987', 'dd-mm-yyyy'), 3000.00, null, 20); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7839, 'KING', 'PRESIDENT', null, to_date('17-11-1981', 'dd-mm-yyyy'), 5000.00, null, 10); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7844, 'TURNER', 'SALESMAN', 7698, to_date('08-09-1981', 'dd-mm-yyyy'), 1500.00, 0.00, 30); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7876, 'ADAMS', 'CLERK', 7788, to_date('23-05-1987', 'dd-mm-yyyy'), 1100.00, null, 20); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7900, 'JAMES', 'CLERK', 7698, to_date('03-12-1981', 'dd-mm-yyyy'), 950.00, null, 30); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7902, 'FORD', 'ANALYST', 7566, to_date('03-12-1981', 'dd-mm-yyyy'), 3000.00, null, 20); insert into emp2 (EMPNO, ENAME, JOB, MGR, HIREDATE, SAL, COMM, DEPTNO) values (7934, 'MILLER', 'CLERK', 7782, to_date('23-01-1982', 'dd-mm-yyyy'), 1300.00, null, 10); ============================================================================================================================= create table dept2 ( deptno number(2), dname varchar2(14), loc varchar2(13) ); ---------------------------------------------------- insert into dept2 (DEPTNO, DNAME, LOC) values (10, 'ACCOUNTING', 'NEW YORK'); insert into dept2 (DEPTNO, DNAME, LOC) values (20, 'RESEARCH', 'DALLAS'); insert into dept2 (DEPTNO, DNAME, LOC) values (30, 'SALES', 'CHICAGO'); insert into dept2 (DEPTNO, DNAME, LOC) values (40, 'OPERATIONS', 'BOSTON'); ============================================================ create table salgrade2 ( grade number, losal number, hisal number ); -------------------------------------------------- insert into salgrade2 (GRADE, LOSAL, HISAL) values (1, 700, 1200); insert into salgrade2 (GRADE, LOSAL, HISAL) values (2, 1201, 1400); insert into salgrade2 (GRADE, LOSAL, HISAL) values (3, 1401, 2000); insert into salgrade2 (GRADE, LOSAL, HISAL) values (4, 2001, 3000); insert into salgrade2 (GRADE, LOSAL, HISAL) values (5, 3001, 9999); ======================================================== select * from emp2; select * from dept2; select * from salgrade2; ===================================== select * from emp2; --employee2 员工表 select * from dept2; --department2 部门表 select * from salgrade2; -- salary grade2 工资等级表 ----------------------------------------------------- emp2 empno 员工编号 ename 员工姓名 job 工作/工种 mgr manager上级编号 hiredate 入职日期 sal salary 工资 comm 奖金/津贴 deptno 部门编号 --------------------- dept2 deptno 部门号 dname 部门名称 loc 所在地 --------------------------- salgrade2 grade 等级 losal lowest salary 最低工资 hisal high salary 最高工资 =============================================
数据查询语句: select from where
查询emp2表中，所有员工的姓名、工资、部门号: select ename,sal,deptno from emp2;
查询emp2表中，工资大于1500 的员工信息: select * from emp2 where sal > 1500;
查询emp2表中，上级是7698 的员工姓名和津贴: select ename,comm from emp2 where mgr = 7698;
列的别名:
select ename,sal,deptno from emp2; select ename 姓名,sal 工资,deptno 部门号 from emp2; select ename as 姓名,sal as 工资,deptno as 部门号 from emp2; select ename as e,sal as s,deptno as d from emp2; select ename as "Esc",sal as "alS",deptno as "dDD" from emp2; select ename as "e%",sal as "s#",deptno as "d()" from emp2;
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算术运算 + - * / （） 支持数值型和日期型(只能加减)数据:
查询每个员工的年薪: select ename,sal,sal*12 from emp2;
给20部门员工，涨薪300之后，工资是多少？: select ename,sal,sal+300 from emp2 where deptno = 20;
查询每名员工的 工资奖金和 : select sal,comm,sal+comm from emp2;
运算中如果有空值，那么最后结果为空 --空值替换 nvl() select sal,comm,nvl(comm,0),sal+nvl(comm,0) from emp2; select * from emp2; insert into emp2(empno) values(1122); delete from emp2 where empno = 1122; select ename,nvl(ename,'未知') from emp2;
连接符 : select ename,sal from emp2; select ename||'的工资是'||sal||'，部门是'||deptno from emp2;
去重
查询emp中，有多少个部门: select distinct deptno from emp2;
查询emp中，有多少种工作 select distinct job from emp2;
where 比较运算符 一般的比较运算符 > >= <= < = != <> 特殊的比较运算符 between……and…… in(……) like …… 像 模糊查询 is null 空值
select * from emp2 where comm is null;
select * from emp2 where comm is not null;
查询工资在1500 到 3000 的员工信息: select * from emp2 where sal between 1500 and 3000; --闭区间 下限 上限
select * from emp2 where sal >= 1500 and sal <= 3000;
查询从事CLERK或SALESMAN 的员工信息: 1）字符串 2）关于大小写 select * from emp2 where job in('CLERK','SALESMAN'); select * from emp2 where job = 'CLERK' or job = 'SALESMAN' ; select * from emp2 where sal in(1500,3000); select * from emp2 where sal = 1500 or sal = 3000;
like select * from emp2 where ename like 'S%';
% sql里的% 等同于linux的* ，代表零个或多个任意字符 _ 代表一个任意字符 select * from emp2 where ename like 'S_ITH'; select t.*,t.rowid from emp2 t; select emp2.*,rowid from emp2;
查询以S%开头的员工信息: select * from emp2 where ename like 'S\%%' escape '\'; escape '\':定义\这个符号后面符号位普通字符串，不是系统里默认的符号。即转义 select * from emp2 where ename like 'S|%%' escape '|'; select * from emp2 where ename like 'S%\%' escape '\';
escape： 用来转译的，比如数据库中有个表 test字段name 中存了字符'%'，那么我查询的时候如果想查询第二位是 '%'的记录就要用到模糊查询，
但是'%'是模糊查询的通配符，我不能如下查询： select * from test where name like '_%%';
这样系统不会把第二个【%】当做字符，只能转译，转译默认的符号是 【\】 select * from test where name like '_\%%';
但是可以自定义转义符，这时候就用 escape，比如定义【*】为转义符 select * from test where name like '_*%%' escape '*';
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逻辑运算符 and or not () 运算优先级：not > and > or ,()优先级最高
查询，20 部门中，从事CLERK 工作的员工: select * from emp2 where deptno = 20 and job = 'CLERK';
查询，30 部门中，奖金为空的员工信息: select * from emp2 where deptno = 30 and comm is null;
查询，除10 部门之外，工资大于1500 的员工信息: select * from emp2 where deptno != 10 and sal > 1500;
查询，工作是SALESMAN ，或工资不小于3000 的员工: select * from emp2 where job = 'SALESMAN' or sal >= 3000;
查询，工作不是SALESMAN ，也不是CLERK 的员工: select * from emp2 where job != 'SALESMAN' and job != 'CLERK'; select * from emp2 where job in('SALESMAN','CLERK'); select * from emp2 where job not in('SALESMAN','CLERK');
查询，工作是SALESMAN，或，工作是PRESIDENT并且工资大于1500的员工信息: select * from emp2 where job = 'SALESMAN' or job = 'PRESIDENT' and sal > 1500;
查询，工作是SALESMAN或PRESIDNET，并且工资大于1500 的员工信息: select * from emp2 where (job = 'SALESMAN' or job = 'PRESIDENT') and sal > 1500; select * from emp2 where job in('SALESMAN','PRESIDENT') and sal > 1500;
order by 排序 select from where order by 列名|别名|算术表达式|函数 order by 列1,别名,函数 order by 列1,列2 desc; order by的位置：在整个查询语句的最后多次排序
select * from emp2 order by sal; --升序 select * from emp2 order by sal asc; --升序 select * from emp2 order by sal desc; --降序 select ename 姓名,job 工作 from emp2 where deptno = 20 order by 姓名 desc;
查询员工信息，结果按照工资奖金和 升序排序: select emp2.*,sal+nvl(comm,0) from emp2 order by sal+nvl(comm,0);
查询员工信息，结果按照部门号排序;如果部门号相同，按照工资降序排序 select * from emp2 order by deptno asc,sal desc;
函数 单组函数 一个值对应一个结果 分组函数/聚合函数 多个值对应一个结果 avg() sum() 单组函数 --字符函数 UPPER() LOWER() INITCAP() ---字母大小写 大写 小写 首字母大写 replace() substr() concat() nvl() nvl2() 替换 截取 连接
select ename,lower(ename),initcap(ename) from emp2; select t.*,t.rowid from emp2 t; select * from emp2 where lower(job) = 'clerk'; select ename,replace(ename,'S','s') from emp2; select ename,substr(ename,2,3) from emp2; 起始位,长度
查询工作名称以SALES 开头的员工信息: select * from emp2 where job like 'SALES%'; select * from emp2 where substr(job,1,5) = 'SALES'; select ename||'的工资是'||sal||deptno from emp2; select concat(ename,sal) from emp2; select concat(concat(ename,'的工资是'),sal) from emp2;
函数是可以嵌套的 select substr(concat(ename,'的工资是'),5,5) from emp2; select comm,nvl(comm,0),nvl2(comm,1000,0) from emp2; 非空替换,空值替换
数值函数 round(x[,y]) 取整或保留指定小数位，规则：四舍五入 trunc(x[,y]) 取整或保留指定小数位，规则：截断 mod(x,y) 取模/取余 round(5.72) = 6 round(5.718,2) = 5.72 round(04.718,-1) = 0 trunc(5.72) = 5 trunc(5.718,2) = 5.71 trunc(05.718,-1) = 0 select round(5.72), round(5.718,2),round(5.718,-1) from dual; select trunc(5.718,2),mod(8,4),mod(10,3) from dual;
dual表 作用：语句补全 select * from dual; select sysdate from dual; select 12*15,round(1000/23,2) from dual; select Sys_Context('userenv','db_name') from dual;--查看当前数据库 名 select Dbms_Random.random from dual;--获得一个随机数 select Dbms_Random.value(10,20) from dual;--获得一个随机数
日期函数 使用insert，新增一条记录： 员工编号：1122 员工工作：SALESMAN 入职日期：2018年7月1号 insert into 表名(列名) values(列对应的值); insert into emp(empno,job,hiredate) values(1122,'SALESMAN','01-7月-18'); insert into emp(empno,job,hiredate) values(1122,'SALESMAN','2018-7-1'); select * from emp; --1)默认日期格式 select * from nls_session_parameters; alter session set NLS_DATE_FORMAT='YYYY-MM-DD'; alter session set NLS_DATE_FORMAT='DD-MON-RR'; --2) 日期函数 to_date(日期，格式) insert into emp(empno,job,hiredate) values(1123,'SALESMAN',to_date('10-1-2018','MM-DD-YYYY')); --查询入职日期早于1981年9 月30 号的员工信息 select from where hiredate < to_date()