扒扒数据库长长知识(下载资源组合看)之 03 (过滤和排序数据)

select ....

from table1

where ....

order by ....

//where

1 有关日期格式属性修改 常识

NLS_DATE_FORMAT DD-MON-RR

select sysdate from dual;

NLS_CURRENCY ￥

SQL> select * from v$nls_parameters;

PARAMETER VALUE

---------------------------------------------------------------- -------------------------------------------

---------

NLS_LANGUAGE SIMPLIFIED CHINESE

NLS_TERRITORY CHINA

NLS_CURRENCY ￥

NLS_ISO_CURRENCY CHINA

NLS_NUMERIC_CHARACTERS .,

NLS_CALENDAR GREGORIAN

NLS_DATE_FORMAT DD-MON-RR

NLS_DATE_LANGUAGE SIMPLIFIED CHINESE

NLS_CHARACTERSET ZHS16GBK

NLS_SORT BINARY

NLS_TIME_FORMAT HH.MI.SSXFF AM

NLS_TIMESTAMP_FORMAT DD-MON-RR HH.MI.SSXFF AM

NLS_TIME_TZ_FORMAT HH.MI.SSXFF AM TZR

NLS_TIMESTAMP_TZ_FORMAT DD-MON-RR HH.MI.SSXFF AM TZR

NLS_DUAL_CURRENCY ￥

NLS_NCHAR_CHARACTERSET AL16UTF16

NLS_COMP BINARY

NLS_LENGTH_SEMANTICS BYTE

NLS_NCHAR_CONV_EXCP FALSE

已选择19行。

alter session set NLS_DATE_FORMAT='DD-MON-RR';

alter session set NLS_DATE_FORMAT='yyyy-mm-dd';

----查询比81年1月1号 入职晚的员工

1 select *

2 from emp

3* where hiredate > '01-1月 -81' //字符串和日期放到''中

SQL> /

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- -------------- ---------- ---------- ----------

7499 ALLEN SALESMAN 7698 20-2月 -81 1600 300 30

7521 WARD SALESMAN 7698 22-2月 -81 1250 500 30

7566 JONES MANAGER 7839 02-4月 -81 2975 20

7654 MARTIN SALESMAN 7698 28-9月 -81 1250 1400 30

7698 BLAKE MANAGER 7839 01-5月 -81 2850 30

7782 CLARK MANAGER 7839 09-6月 -81 2450 10

7788 SCOTT ANALYST 7566 19-4月 -87 3000 20

7839 KING PRESIDENT 17-11月-81 5000 10

7844 TURNER SALESMAN 7698 08-9月 -81 1500 0 30

7876 ADAMS CLERK 7788 23-5月 -87 1100 20

7900 JAMES CLERK 7698 03-12月-81 950 30

7902 FORD ANALYST 7566 03-12月-81 3000 20

7934 MILLER CLERK 7782 23-1月 -82 1300 10

已选择13行。

------- oracle支持 隐式类型转换 ..eg char ****====>date,抛砖

-------- 日期转换的函数.....

------ 日期和字符串''

-------日期是格式敏感

----select ....

----from .....

----where col > 30 //（col是列名，第一个一定是列名）

col in ()

col between a and b .. // a要小b [] (闭区间)

1 查询工资在1000~2000之间的员工信息

select *

from emp

where sal between 1000 and 2000

select *

from emp

where sal >=1000 and sal <=2000

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- -------------- ---------- ---------- ----------

7499 ALLEN SALESMAN 7698 20-2月 -81 1600 300 30

7521 WARD SALESMAN 7698 22-2月 -81 1250 500 30

7654 MARTIN SALESMAN 7698 28-9月 -81 1250 1400 30

7844 TURNER SALESMAN 7698 08-9月 -81 1500 0 30

7876 ADAMS CLERK 7788 23-5月 -87 1100 20

7934 MILLER CLERK 7782 23-1月 -82 1300 10

1 select *

2 from emp

3* where sal between 1000 and 200

SQL> /

2 查询10 20号部门的员工信息

查询不是10 20号部门的员工信息

select * from emp

where DEPTNO in (10, 20)

select * from emp

where DEPTNO not in (10, 20)

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- -------------- ---------- ---------- ----------

7369 SMITH CLERK 7902 17-12月-80 800 20

7566 JONES MANAGER 7839 02-4月 -81 2975 20

7782 CLARK MANAGER 7839 09-6月 -81 2450 10

7788 SCOTT ANALYST 7566 19-4月 -87 3000 20

7839 KING PRESIDENT 17-11月-81 5000 10

7876 ADAMS CLERK 7788 23-5月 -87 1100 20

7902 FORD ANALYST 7566 03-12月-81 3000 20

7934 MILLER CLERK 7782 23-1月 -82 1300 10

3 in 中是一个集合 .....null

select * from emp

where DEPTNO in (10, 20, null)

select * from emp

where DEPTNO not in (10, 20)

======> in集合中遇见null (in集合和空值在一起...)

=====>in (集合中含有空值 ) 查询结果不受影响

======>not in (集合中含有空值 ) 查询结果受影响

why? 思考题

=====> day02下午....

4 like模糊查询

% 代表零个或多个字符(任意个字符)。

_ 代表一个字符。

查询名字S开头的员工信息

1 select * from emp

2* where ENAME like 'S%'

---''单引号中的字符串是区分大小写的....

SQL> /

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- -------------- ---------- ---------- ----------

7369 SMITH CLERK 7902 17-12月-80 800 20

7788 SCOTT ANALYST 7566 19-4月 -87 3000 20

查询名字含有4个字母的员工

select * from emp

where ENAME like '____'

1 select * from emp

2* where ENAME like '____'

SQL> /

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- -------------- ---------- ---------- ----------

7521 WARD SALESMAN 7698 22-2月 -81 1250 500 30

7839 KING PRESIDENT 17-11月-81 5000 10

7902 FORD ANALYST 7566 03-12月-81 3000 20

查询名字含有下划线的员工 (查询的内容含有转义字符)

insert into emp(empno, ename, sal , DEPTNO) values(1, 'tom_abc', 8000, 10)

select * from emp

where ename like '%\_%' escape '\'

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- -------------- ---------- ---------- ----------

1 tom_abc 8000 10

=================ORDER BY子句=============================

1 order by 默认按照排序 从小到大

2 order by后面+列名 表达式 别名 序号

按照薪水,查询员工信息

select *from emp

order by sal

select empno, ename, sal, sal*12 年薪 from emp

order by 年薪

1 select empno, ename, sal, sal*12 年薪 from emp

2* order by 年薪

SQL> /

EMPNO ENAME SAL 年薪

---------- ---------- ---------- ----------

7369 SMITH 800 9600

7900 JAMES 950 11400

7876 ADAMS 1100 13200

7521 WARD 1250 15000

7654 MARTIN 1250 15000

7934 MILLER 1300 15600

7844 TURNER 1500 18000

7499 ALLEN 1600 19200

7782 CLARK 2450 29400

7698 BLAKE 2850 34200

7566 JONES 2975 35700

7902 FORD 3000 36000

7788 SCOTT 3000 36000

7839 KING 5000 60000

1 tom_abc 8000 96000

按照年薪,查询员工信息

2 order by 遇上空值

1 任何表达式和null运算都为空

2 null != null (is null )

3 where子句中(in集合和空值在一起...)

4

按照奖金,查询员工信息

1 select empno, ename, comm from emp

2 order by 3 desc

3* nulls last

SQL> /

EMPNO ENAME COMM

---------- ---------- ----------

7654 MARTIN 1400

7521 WARD 500

7499 ALLEN 300

7844 TURNER 0

7782 CLARK

7788 SCOTT

7839 KING

7876 ADAMS

7900 JAMES

7902 FORD

7698 BLAKE

7566 JONES

7934 MILLER

1 tom_abc

7369 SMITH

已选择15行。

3 order by 后面有多个列,

如果多个列中 有desc修饰,只作用于最近的那一列

按照部门排序

select * from emp

order by deptno desc, sal desc;

按照部门和工资排序

select * from emp

order by deptno desc, sal desc

/

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

---------- ---------- --------- ---------- -------------- ---------- ---------- ----------

7698 BLAKE MANAGER 7839 01-5月 -81 2850 30

7499 ALLEN SALESMAN 7698 20-2月 -81 1600 300 30

7844 TURNER SALESMAN 7698 08-9月 -81 1500 0 30

7521 WARD SALESMAN 7698 22-2月 -81 1250 500 30

7654 MARTIN SALESMAN 7698 28-9月 -81 1250 1400 30

7900 JAMES CLERK 7698 03-12月-81 950 30

7902 FORD ANALYST 7566 03-12月-81 3000 20

7788 SCOTT ANALYST 7566 19-4月 -87 3000 20

7566 JONES MANAGER 7839 02-4月 -81 2975 20

7876 ADAMS CLERK 7788 23-5月 -87 1100 20

7369 SMITH CLERK 7902 17-12月-80 800 20

1 tom_abc 8000 10

7839 KING PRESIDENT 17-11月-81 5000 10

7782 CLARK MANAGER 7839 09-6月 -81 2450 10

7934 MILLER CLERK 7782 23-1月 -82 1300 10

已选择15行。