Oracle常用知识总结

2022-10-13 23:12:04

1.曾经不小心把开发库的数据库表全部删除，当时吓的要死。结果找到下面的语句恢复到了1个小时之前的数据！很简单。

注意使用管理员登录系统：

select * from 表名 as of timestamp sysdate-1/12 //查询两个小时前的某表数据！既然两小时以前的数据都得到了，继续怎么做，知道了吧。。

如果drop了表，怎么办？？见下面：

drop table 表名;

数据库误删除表之后恢复,不过要记得删除了哪些表名。

flashback table 表名 to before drop;

2.查询得到当前数据库中锁，以及解锁：

查锁

SELECT s.username,

decode(l.type,‘TM‘,‘TABLE LOCK‘,

‘TX‘,‘ROW LOCK‘,

NULL) LOCK_LEVEL,

o.owner,o.object_name,o.object_type,

s.sid,s.serial#,s.terminal,s.machine,s.program,s.osuser

FROM v$session s,v$lock l,dba_objects o

WHERE l.sid = s.sid

AND l.id1 = o.object_id(+)

AND s.username is NOT NULL;

解锁

alter system kill session ‘sid,serial‘;

如果解不了。直接倒os下kill进程kill －9 spid

ORA-28000:账户被锁定

因为密码输入错误多次用户自动被锁定.

解决办法:alter user user_name account unlock;

3.关于查询数据库用户，权限的相关语句：

查看所有用户：

select * from dba_user;

select * from all_users;

select * from user_users;

查看用户系统权限：

select * from dba_sys_privs;

select * from all_sys_privs;

10.select * from user_sys_privs;

查看用户对象权限：

select * from dba_tab_privs;

select * from all_tab_privs;

select * from user_tab_privs;

查看所有角色：

20.select * from dba_roles;

查看用户所拥有的角色：

select * from dba_role_privs;

select * from user_role_privs;

几个经常用到的oracle视图：注意表名使用大写....................

查询oracle中所有用户信息

select * from dba_user;

只查询用户和密码

select username,password from dba_users;

查询当前用户信息

select * from dba_ustats;

查询用户可以访问的视图文本

select * from dba_varrays;

查询数据库中所有视图的文本

select * from dba_views;

查询全部索引

select * from user_indexes;

查询全部表格

select * from user_tables;

查询全部约束

select * from user_constraints;

查询全部对象

select * from user_objects;

查看当前数据库中正在执行的语句，然后可以继续做很多很多事情，例如查询执行计划等等

(1).查看相关进程在数据库中的会话

Select a.sid,a.serial#,a.program, a.status ,

substr(a.machine,1,20), a.terminal,b.spid

from v$session a, v$process b

where a.paddr=b.addr

and b.spid = &spid;

(2).查看数据库中被锁住的对象和相关会话

select a.sid,a.serial#,a.username,a.program,

c.owner, c.object_name

from v$session a, v$locked_object b, all_objects c

where a.sid=b.session_id and

c.object_id = b.object_id;

(3).查看相关会话正在执行的SQL

select sql_text from v$sqlarea where address =

( select sql_address from v$session where sid = &sid );

(1).查看相关进程在数据库中的会话

Select a.sid,a.serial#,a.program, a.status ,

substr(a.machine,1,20), a.terminal,b.spid

from v$session a, v$process b

where a.paddr=b.addr

and b.spid = &spid;

(2).查看数据库中被锁住的对象和相关会话

select a.sid,a.serial#,a.username,a.program,

c.owner, c.object_name

from v$session a, v$locked_object b, all_objects c

where a.sid=b.session_id and

c.object_id = b.object_id;

(3).查看相关会话正在执行的SQL

select sql_text from v$sqlarea where address =

( select sql_address from v$session where sid = &sid );

查询表的结构：表名大写！！

select t.COLUMN_NAME,

t.DATA_TYPE,

nvl(t.DATA_PRECISION, t.DATA_LENGTH),

nvl(T.DATA_SCALE, 0),

c.comments

from all_tab_columns t, user_col_comments c

whEre t.TABLE_NAME = c.table_name

and t.COLUMN_NAME = c.column_name

and t.TABLE_NAME = UPPER(‘OM_EMPLOYEE_T‘)

order by t.COLUMN_ID

行列互换：

Sql代码

建立一个例子表：

CREATE TABLE t_col_row(

ID INT,

c1 VARCHAR2(10),

c2 VARCHAR2(10),

c3 VARCHAR2(10));

INSERT INTO t_col_row VALUES (1, ‘v11‘, ‘v21‘, ‘v31‘);

INSERT INTO t_col_row VALUES (2, ‘v12‘, ‘v22‘, NULL);

INSERT INTO t_col_row VALUES (3, ‘v13‘, NULL, ‘v33‘);

INSERT INTO t_col_row VALUES (4, NULL, ‘v24‘, ‘v34‘);

INSERT INTO t_col_row VALUES (5, ‘v15‘, NULL, NULL);

INSERT INTO t_col_row VALUES (6, NULL, NULL, ‘v35‘);

INSERT INTO t_col_row VALUES (7, NULL, NULL, NULL);

COMMIT;

下面的是列转行:创建了一个视图

CREATE view v_row_col AS

SELECT id, ‘c1‘ cn, c1 cv

FROM t_col_row

UNION ALL

SELECT id, ‘c2‘ cn, c2 cv

FROM t_col_row

UNION ALL

SELECT id, ‘c3‘ cn, c3 cv FROM t_col_row;

下面是创建了没有空值的一个竖表:

CREATE view v_row_col_notnull AS

SELECT id, ‘c1‘ cn, c1 cv

FROM t_col_row

where c1 is not null

UNION ALL

SELECT id, ‘c2‘ cn, c2 cv

FROM t_col_row

where c2 is not null

UNION ALL

SELECT id, ‘c3‘ cn, c3 cv

FROM t_col_row

where c3 is not null;

Sql代码

建立一个例子表：

CREATE TABLE t_col_row(

ID INT,

c1 VARCHAR2(10),

c2 VARCHAR2(10),

c3 VARCHAR2(10));

INSERT INTO t_col_row VALUES (1, ‘v11‘, ‘v21‘, ‘v31‘);

INSERT INTO t_col_row VALUES (2, ‘v12‘, ‘v22‘, NULL);

INSERT INTO t_col_row VALUES (3, ‘v13‘, NULL, ‘v33‘);

INSERT INTO t_col_row VALUES (4, NULL, ‘v24‘, ‘v34‘);

INSERT INTO t_col_row VALUES (5, ‘v15‘, NULL, NULL);

INSERT INTO t_col_row VALUES (6, NULL, NULL, ‘v35‘);

INSERT INTO t_col_row VALUES (7, NULL, NULL, NULL);

COMMIT;

下面的是列转行:创建了一个视图

CREATE view v_row_col AS

SELECT id, ‘c1‘ cn, c1 cv

FROM t_col_row

UNION ALL

SELECT id, ‘c2‘ cn, c2 cv

FROM t_col_row

UNION ALL

SELECT id, ‘c3‘ cn, c3 cv FROM t_col_row;

下面是创建了没有空值的一个竖表:

CREATE view v_row_col_notnull AS

SELECT id, ‘c1‘ cn, c1 cv

FROM t_col_row

where c1 is not null

UNION ALL

SELECT id, ‘c2‘ cn, c2 cv

FROM t_col_row

where c2 is not null

UNION ALL

SELECT id, ‘c3‘ cn, c3 cv

FROM t_col_row

where c3 is not null;

建立一个例子表：

CREATE TABLE t_col_row(

ID INT,

c1 VARCHAR2(10),

c2 VARCHAR2(10),

c3 VARCHAR2(10));

INSERT INTO t_col_row VALUES (1, ‘v11‘, ‘v21‘, ‘v31‘);

INSERT INTO t_col_row VALUES (2, ‘v12‘, ‘v22‘, NULL);

INSERT INTO t_col_row VALUES (3, ‘v13‘, NULL, ‘v33‘);

INSERT INTO t_col_row VALUES (4, NULL, ‘v24‘, ‘v34‘);

INSERT INTO t_col_row VALUES (5, ‘v15‘, NULL, NULL);

INSERT INTO t_col_row VALUES (6, NULL, NULL, ‘v35‘);

INSERT INTO t_col_row VALUES (7, NULL, NULL, NULL);

COMMIT;

下面的是列转行:创建了一个视图

CREATE view v_row_col AS

SELECT id, ‘c1‘ cn, c1 cv

FROM t_col_row

UNION ALL

SELECT id, ‘c2‘ cn, c2 cv

FROM t_col_row

UNION ALL

SELECT id, ‘c3‘ cn, c3 cv FROM t_col_row;

下面是创建了没有空值的一个竖表:

CREATE view v_row_col_notnull AS

SELECT id, ‘c1‘ cn, c1 cv

FROM t_col_row

where c1 is not null

UNION ALL

SELECT id, ‘c2‘ cn, c2 cv

FROM t_col_row

where c2 is not null

UNION ALL

SELECT id, ‘c3‘ cn, c3 cv

FROM t_col_row

where c3 is not null;

下面可能是dba经常使用的oracle视图吧。呵呵

Sql代码

示例：已知hash_value:3111103299，查询sql语句：

select * from v$sqltext

where hashvalue=‘3111103299‘

order by piece

查看消耗资源最多的SQL：

SELECT hash_value, executions, buffer_gets, disk_reads, parse_calls

FROM V$SQLAREA

WHERE buffer_gets > 10000000OR disk_reads > 1000000

ORDERBY buffer_gets + 100 * disk_reads DESC;

查看某条SQL语句的资源消耗：

SELECT hash_value, buffer_gets, disk_reads, executions, parse_calls

FROM V$SQLAREA

WHERE hash_Value = 228801498AND address = hextoraw(‘CBD8E4B0‘);

查询sql语句的动态执行计划:

首先使用下面的语句找到语句的在执行计划中的address和hash_code

SELECT sql_text, address, hash_value FROM v$sql t

where (sql_text like ‘%FUNCTION_T(表名大写!)%‘)

然后:

SELECT operation, options, object_name, cost FROM v$sql_plan

WHERE address = ‘C00000016BD6D248‘ AND hash_value = 664376056;

查询oracle的版本:

select * from v$version;

查询数据库的一些参数:

select * from v$parameter

查找你的session信息

SELECT SID, OSUSER, USERNAME, MACHINE, PROCESS

FROM V$SESSION WHERE audsid = userenv(‘SESSIONID‘);

当machine已知的情况下查找session

SELECT SID, OSUSER, USERNAME, MACHINE, TERMINAL

FROM V$SESSION

WHERE terminal = ‘pts/tl‘ AND machine = ‘rgmdbs1‘;

查找当前被某个指定session正在运行的sql语句。假设sessionID为100

select b.sql_text

from v$session a,v$sqlarea b

where a.sql_hashvalue=b.hash_value and a.sid=100

Sql代码

示例：已知hash_value:3111103299，查询sql语句：

select * from v$sqltext

where hashvalue=‘3111103299‘

order by piece

查看消耗资源最多的SQL：

SELECT hash_value, executions, buffer_gets, disk_reads, parse_calls

FROM V$SQLAREA

WHERE buffer_gets > 10000000OR disk_reads > 1000000

ORDERBY buffer_gets + 100 * disk_reads DESC;

查看某条SQL语句的资源消耗：

SELECT hash_value, buffer_gets, disk_reads, executions, parse_calls

FROM V$SQLAREA

WHERE hash_Value = 228801498AND address = hextoraw(‘CBD8E4B0‘);

查询sql语句的动态执行计划:

首先使用下面的语句找到语句的在执行计划中的address和hash_code

SELECT sql_text, address, hash_value FROM v$sql t

where (sql_text like ‘%FUNCTION_T(表名大写!)%‘)

然后:

SELECT operation, options, object_name, cost FROM v$sql_plan

WHERE address = ‘C00000016BD6D248‘ AND hash_value = 664376056;

查询oracle的版本:

select * from v$version;

查询数据库的一些参数:

select * from v$parameter

查找你的session信息

SELECT SID, OSUSER, USERNAME, MACHINE, PROCESS

FROM V$SESSION WHERE audsid = userenv(‘SESSIONID‘);

当machine已知的情况下查找session

SELECT SID, OSUSER, USERNAME, MACHINE, TERMINAL

FROM V$SESSION

WHERE terminal = ‘pts/tl‘ AND machine = ‘rgmdbs1‘;

查找当前被某个指定session正在运行的sql语句。假设sessionID为100

select b.sql_text

from v$session a,v$sqlarea b

where a.sql_hashvalue=b.hash_value and a.sid=100

示例：已知hash_value:3111103299，查询sql语句：

select * from v$sqltext

where hashvalue=‘3111103299‘

order by piece

查看消耗资源最多的SQL：

SELECT hash_value, executions, buffer_gets, disk_reads, parse_calls

FROM V$SQLAREA

WHERE buffer_gets > 10000000OR disk_reads > 1000000

ORDERBY buffer_gets + 100 * disk_reads DESC;

查看某条SQL语句的资源消耗：

SELECT hash_value, buffer_gets, disk_reads, executions, parse_calls

FROM V$SQLAREA

WHERE hash_Value = 228801498AND address = hextoraw(‘CBD8E4B0‘);

查询sql语句的动态执行计划:

首先使用下面的语句找到语句的在执行计划中的address和hash_code

SELECT sql_text, address, hash_value FROM v$sql t

where (sql_text like ‘%FUNCTION_T(表名大写!)%‘)

然后:

SELECT operation, options, object_name, cost FROM v$sql_plan

WHERE address = ‘C00000016BD6D248‘ AND hash_value = 664376056;

查询oracle的版本:

select * from v$version;

查询数据库的一些参数:

select * from v$parameter

查找你的session信息

SELECT SID, OSUSER, USERNAME, MACHINE, PROCESS

FROM V$SESSION WHERE audsid = userenv(‘SESSIONID‘);

当machine已知的情况下查找session

SELECT SID, OSUSER, USERNAME, MACHINE, TERMINAL

FROM V$SESSION

WHERE terminal = ‘pts/tl‘ AND machine = ‘rgmdbs1‘;

查找当前被某个指定session正在运行的sql语句。假设sessionID为100

select b.sql_text

from v$session a,v$sqlarea b

where a.sql_hashvalue=b.hash_value and a.sid=100

树形结构connect by 排序：

Sql代码

查询树形的数据结构，同时对一层里面的数据进行排序

SELECT last_name, employee_id, manager_id, LEVEL

FROM employees

START WITH employee_id = 100

CONNECT BY PRIOR employee_id = manager_id

ORDER SIBLINGS BY last_name;

下面是查询结果

LAST_NAME EMPLOYEE_ID MANAGER_ID LEVEL

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

King 100 1

Cambrault 148 100 2

Bates 172 148 3

Bloom 169 148 3

Fox 170 148 3

Kumar 173 148 3

Ozer 168 148 3

Smith 171 148 3

De Haan 102 100 2

Hunold 103 102 3

Austin 105 103 4

Ernst 104 103 4

Lorentz 107 103 4

Pataballa 106 103 4

Errazuriz 147 100 2

Ande 166 147 3

Banda 167 147 3

Sql代码

查询树形的数据结构，同时对一层里面的数据进行排序

SELECT last_name, employee_id, manager_id, LEVEL

FROM employees

START WITH employee_id = 100

CONNECT BY PRIOR employee_id = manager_id

ORDER SIBLINGS BY last_name;

下面是查询结果

LAST_NAME EMPLOYEE_ID MANAGER_ID LEVEL

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

King 100 1

Cambrault 148 100 2

Bates 172 148 3

Bloom 169 148 3

Fox 170 148 3

Kumar 173 148 3

Ozer 168 148 3

Smith 171 148 3

De Haan 102 100 2

Hunold 103 102 3

Austin 105 103 4

Ernst 104 103 4

Lorentz 107 103 4

Pataballa 106 103 4

Errazuriz 147 100 2

Ande 166 147 3

Banda 167 147 3

查询树形的数据结构，同时对一层里面的数据进行排序

SELECT last_name, employee_id, manager_id, LEVEL

FROM employees

START WITH employee_id = 100

CONNECT BY PRIOR employee_id = manager_id

ORDER SIBLINGS BY last_name;

下面是查询结果

LAST_NAME EMPLOYEE_ID MANAGER_ID LEVEL

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

King 100 1

Cambrault 148 100 2

Bates 172 148 3

Bloom 169 148 3

Fox 170 148 3

Kumar 173 148 3

Ozer 168 148 3

Smith 171 148 3

De Haan 102 100 2

Hunold 103 102 3

Austin 105 103 4

Ernst 104 103 4

Lorentz 107 103 4

Pataballa 106 103 4

Errazuriz 147 100 2

Ande 166 147 3

Banda 167 147 3

有时候写多了东西，居然还忘记最基本的sql语法，下面全部写出来，基本的oracle语句都在这里可以找到了。是很基础的语句！

Sql代码

在数据字典查询约束的相关信息：

SELECT constraint_name, constraint_type,search_condition

FROM user_constraints WHERE table_name = ‘EMPLOYEES‘;

//这里的表名都是大写！

2对表结构进行说明：

desc Tablename

3查看用户下面有哪些表

select table_name from user_tables;

4查看约束在那个列上建立：

SELECT constraint_name, column_name

FROM user_cons_columns

WHERE table_name = ‘EMPLOYEES‘;

10结合变量查找相关某个表中约束的相关列名：

select constraint_name,column_name from user_cons_columns where table_name = ‘&tablename‘

12查询数据字典看中间的元素：

SELECT object_name, object_type

FROM user_objects

WHERE object_name LIKE ‘EMP%‘

OR object_name LIKE ‘DEPT%‘

14查询对象类型：

SELECT DISTINCT object_type FROM user_objects ;

17改变对象名：（表名，视图,序列）

rename emp to emp_newTable

18添加表的注释：

COMMENT ON TABLE employees IS ‘Employee Information‘;

20查看视图结构：

describe view_name

23在数据字典中查看视图信息：

select viewe_name,text from user_views

25查看数据字典中的序列：

select * from user_sequences

33得到所有的时区名字信息：

select * from v$timezone_names

34显示对时区‘US/Eastern’的时区偏移量

select TZ_OFFSET(‘US/Eastern‘) from DUAL--dual英文意思是‘双重的’

显示当前会话时区中的当前日期和时间:

ALTER SESSION SET NLS_DATE_FORMAT = ‘DD-MON-YYYY HH24:MI:SS‘;--修改显示时间的方式的设置

ALTER SESSION SET TIME_ZONE = ‘-5:0‘;--修改时区

SELECT SESSIONTIMEZONE, CURRENT_DATE FROM DUAL;--真正有用的语句！

SELECT CURRENT_TIMESTAMP FROM DUAL;--返回的时间是当前日期和时间，含有时区

SELECT CURRENT_TIMESTAMP FROM DUAL;--返回的时间是当前日期和时间，不含有时区！！！

35显示数据库时区和会话时区的值：

select datimezone,sessiontimezone from dual;

13普通的建表语句：

CREATE TABLE dept

(deptno NUMBER(2),

dname VARCHAR2(14),

loc VARCHAR2(13));

15使用子查询建立表:

CREATE TABLE dept80

AS SELECT employee_id, last_name,

salary*12 ANNSAL,

hire_date FROM employees WHERE department_id = 80;

6添加列：// alter table EMP add column (dept_id number(7))；错误！！

alter table EMP add (dept_id number(7));

7删除一列：

alter table emp drop column dept_id;

8添加列名同时和约束：

alter table EMP add (dept_id number(7)

constraint my_emp_dept_id_fk references dept(ID));

9改变列：//注意约束不能够修改的！！

alter table dept80 modify(last_name varchar2(30));//这里使用的是modify而不是alter!

24增加一行：

insert into table_name values();

5添加主键:

alter Table EMP add constraint my_emp_id_pk primary key (ID);

11添加一个有check约束的新列：

alter table EMP

add (COMMISSION number(2) constraint emp_commission_ck check(commission>0))

16删除表：

drop table emp;

19创建视图：

CREATE VIEW empvu80

AS SELECT employee_id, last_name, salary

FROM employees WHERE department_id = 80;

21删除视图：

drop view view_name

22找到工资最高的5个人。（top-n分析）（行内视图）

select rownum,employee_id from (select employee_id,salary from

employees order by salary desc)

where rownum<5;

26建立同义词：

create synonym 同义词名 for 原来的名字

或者 create public synonym 同义词名 for 原来的名字

27建立序列：（注意，这里并没有出现说是哪个表里面的序列！！）

CREATE SEQUENCE dept_deptid_seq

INCREMENT BY 10

START WITH 120

MAXVALUE 9999

NOCACHE

NOCYCLE

28使用序列：

insert into dept(ID,NAME) values(DEPT_ID_SEQ.nextval,‘Administration‘);

29建立索引：//默认就是nonunique索引，除非使用了关键字：unique

CREATE INDEX emp_last_name_idx ON employees(last_name);

30建立用户：（可能有错，详细查看帮助）

create user username(用户名)

identified by oracle(密码)

default tablespace data01(表空间名//默认存在system表空间里面)

Oracle常用知识总结

码农公寓

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