Oracle数据库实例教程

 

1. Writing Basic SQL Select Statements

Operator

+, - , *, /, ()  parentheses

 

Nul values在算术表达式中，结果为null

 

desc tablename 查看table structure

 

2. Restricting and Sorting Data

Comparision Conidtions

=, > , >=, <, <=, <>

between ... and ...

In(set)

like     %  _

is null

 

Logical Conidtions

AND, OR, NOT

 

ASC, DESC

 

 

3. Single-Row Functions

1). Character Functions

lower

upper

initcap: 单词首字母大写

concat

substr

length

instr

lpad(salary,10,'*')     *****24000

rpad

trim('H' from 'HelloWorld')          elloWorld

replace

 

 

2). Number Functions

round(45.926,2)        45.93

trunc(45.926,2)         45.92

mod(1600,300)          100

 

 

3). Date Functions

default format:   DD-MON-RR

 

select sysdate from dual;

 

MONTHS_BETWEEN

ADD_MONTHS

NEXT_DAY

LAST_DAY

ROUND

TRUNC

 

4). Conversion Functions

(1) char to number

(2) char to date

(3) number to char

(4) date to varchar

 

to_char(date,'format_model')

YYYY, YEAR, MM, MONTH, MON,DY,DAY,DD

HH24:MI:SS AM/PM

to_char(number,'format_model')

9:    Represents a number

0:    Forces a zero to be displayed

$:    Places a floating dollar sign

L:    Use the floating local currency symbol

.:     Prints a decimal point

,:     Prints a thousand indicator

to_number(char,'format_model')

to_date(char,'format_model')

 

 

5). General Functions

NVL(expr1,expr2)

NVL2(expr1,expr2,expr3)

NULLIF(expr1,expr2)

COALESCE(expr1,expr2,...,exprn)

 

6). Conditional Functions

CASE expr WHEN  expr1 THEN return_expr1

WHEN  expr2 THEN return_expr2

... ...

ELSE else_expr

END

 

DECODE (exp, search1, result1, search2,result2...,default)

 

4. Display Data from Multiple Tables

左外连接，（+）在右边

 

自连接

 

left outer join on ...

right outer join on ...

full outer join

 

 

5. Aggregating Data Using Group Functions

 avg

count

max

min

sum

stddev：标准偏差

variance：标准方差

 

Having 子句

  

 

6. Subqueries

 Single-Row Subqueries

 =,>,>=,<,<=,<>

 Multiple-Row Subqueries

 In, Any, All

7. Producing Readable Output with iSQL*Plus

select * from fmvat where unid = &a;

替换变量参数

SQL> define a=7

SQL> select * from fmvat where unid = &a;

SQL> define

查看已定义变量

SQL>undefine

SQL>select &&b from fmvat where unid = &b; 避免重复定义

SQL> set verify on
SQL> select &&b from fmvat where unid = &b;
&b: 7
&b: 7

         7
----------
         7

SQL> set system_variable value

SQL> set echo on

SQL> show all       显示所有环境变量

SQL> show echo   显示当前环境变量

SQL> help show(set)

8. Manipulating Data

 default 值： create table的时候定义

insert into test2 values(1, default)

update test2 set xxx=default

merge into tablea : 没有就insert，有就update

commit

savepoint

rollback to savepoint

9. Creating and Managing Tables

select * from user_tables;
select * from user_objects;
select * from user_catalog;

select * from dba_tables;
select * from dba_objects;
select * from dba_catalog;

select * from all_tables;
select * from all_objects;
select * from all_catalog;

数据类型

Varchar2(size)

char(size)

number(p,s)

Date

LONG

CLOB

RAW and LONG RAW

BLOB

BFILE

bfile字段实际的文件存储在文件系统中,字段中存储的是文件定位指针.bfile对oracle来说是只读的,也不参与事务性控制和数据恢复
CREATE or REPLACE DIRECTORY MyDir as 'c:\\bfiles'

GRANT READ ON DIRECTORY MyDir  TO scott;

CREATE TABLE MyBFileTable(col1 number, col2 BFILE)

INSERT INTO MyBFileTable values ('2', BFILENAME('MyDir',"+"'MyFile.jpg'))

ROWID         64 base number

Timestamp

create table tabelname[col1,col2...] as subquery;

alter table tablename add (column datatype defaut expr1, ...;

alter table tablename modify  (column datatype default expr1,...;

alter table tablename drop column;

alter table tablename set unused(column);

alter table tablename drop unused columns;

drop table tablename;

rename dataobject to anothername;

truncate table tablename;    DDL

comment on table/view xxx is 'xxx xxx xxx';

all_col_comments

user_col_comments

all_tab_comments

user_tab_comments

comment on column FMVAT.VATCODE is 'VAT code ';

10. Including Constraints

Not null

Unique

Primary Key

Foreign Key

Check

create table test1

(id int not null,

lname varchar(20),

constraint  uk_test1_1 unique(lname,fname));

alter table test add constraint primary key(unid);

alter table test add constraint foreign key(id) references xxx(unid);

on delete cascade

on delete set null

alter table test3 add constraint ck_test3_1 check(name like 'k%');

alter table test4 drop constraint pK_test_1 cascade;

alter table test5 disable/enable constraint pK_test_1 cascade;

alter table test6 drop pk cascade constraints;

数据字典：  user_constraints, user_cons_column

11. Create Views

set wrap off

set linesize 1000

create or replace view testview1 as select * from test;

create force view testview1 as select * from test;

create force view testview1 as select * from test

where qty > 10

with check option (constraint empvu20_ck);

with read only

Top-N  Analysis

select column_list, rownum

from (select column_list from table order by Top-N_column)

where rownum <= N;

12. Create Indexs, Sequence, Synonym

 (1) Sequence

Create sequence  se1

[increment by n]

[start with n]

[maxvalue n | nomaxvalue]

[minvalue n | nominvalue]

[cycle | nocycle]

[cache n | nocache]

 

 

数据字典：user_sequences

 

 se1.nextvalue

 se1.currval

 

alter sequence xxx ...

drop sequence xxx

 

 (2) Index

 

create index xxx on table (col1,col2,...)

 

When to Create an Index

(1) A column contains a wide range of values

(2) One or more columns are frequently used together in a where clause or a join condition

(3) The table is large and most queries are expected to retrieve 20% of whole rows.

 

When not to create an Index

The indexed columsn are referenced as part of an expression

 

数据字典：user_indexes,   user_ind_columns

 

function-Based Indexes

 

create index xxx idx on table(upper(au_fname)

 

 

 (3) Synonyms

 

create [public] synonym xxx for object;

 

 

 

13. Control user access

 create users

 

 create user scott identified by tiger;

 

 grant privilege,... to user|role,PUBLIC...

 

 create session

 create table

 create sequence

 create view

 create procedure

 

 create role manager;

 grant create table,create view to manager;

 grant manager to usera,userb...;

 

 alter user scott identified by lion;

 

 对象权限

grant select（col1，col2） on authors to kxf;

with grant options;  允许传递

 

revork ... from ...  

cascade constraints;  取消传递的权限

 

Database Links：

 

create public database link "linkname" using 'sales'

 

 CREATE DATABASE LINK数据库链接名CONNECT TO 用户名 IDENTIFIED BY 密码 USING ‘本地配置的数据的实例名’;

 

查询远端数据库里的表
            SELECT …… FROM 表名@数据库链接名;

 

 

 

15. Using Set Operator

 union(排序，distinct)/union all

 

 intersect（distinct）

 

 minus （distinct）

 

 需要显示的指定Order by

 

 

16. Datatime Function

 TZ_OFFSET

 CURRENT_DATE

 

 alter session set nls_data_format = 'DD MON YYYY HH24:MI:SS'

 alter session set time_zone='-5:0'

 select sessiontimezone, current_date from dual;

 

 

 CURRENT_TIMESTAMP

 

  select current_timestamp, localtimestamp from dual;

 

   dbtimezone, sessiontimezone

 

 

17. Enhancements to the Group by Clause

 group by [rollup] [cube]

 

 grouping(expr)   结果是0，1 判断是不是聚合的结果

 

 grouping sets example:

select departmetn_id,job_id,manager_id,avg(salary)

from employees

group by grouping sets

((department_id,job_id),(job_id,manager_id));

 

rollup(a, (b,c))

 

18. Advanced Subqueries

where (a,b) in (select a,b...)

 

关联子查询： where exists

 

update，delete中也可以使用子查询

 

with Clause example：

 

with xxx as (select ...)

xxx以后就可以直接用了

 

 

19. Hierarchical Retrieval

Walking the Tree

... ...

from employees

start with employee_id = 101

connect by prior manager_id = employee_id;

 

20. Extensions to DML and DDL Statements

 Insert All

    into table1 values(xxx,xxx,xxx)

    into table2 values(xxx,xxx,xxx)

  select xxx,xxx,xxx from ...

 

 Insert All

    When sal > 1000 then

        into table1 values(xxx,xxx,xxx)

  When mgr > 200 then

    into table2 values(xxx,xxx,xxx)

  select xxx,xxx,xxx from ...

 

Insert First

 

Pivoting Insert: 旋转插入

把一个表的一行分别插入到多个表的每一行

 

扩展表： 数据放在文本文件里面

 

create diretory xxx as 'c:\oracle'