sql语句

SQL> create table t as select * from dba_objects;  数据字典

SQL> desc t;

SQL> select owner from t where rownum <=10; 伪列  rowid

SQL> select count(*) from t;

伪列 rowid,rownum

SQL> delete from t where rownum<=10000;（删除t表10000行）

SQL> select OBJECT_NAME,OBJECT_ID  from t order by OBJECT_ID desc(倒序)

SQL> select * from t order by OBJECT_ID asc (正序)

SQL> select count(*),owner from t group by owner;(分组)

 where   group by    having 

SQL> update t set owner='abc' where OBJECT_ID=51073;

运算符:

等于 = 

大于 >

小于 <

大于等于 >=

小于等于 <=

不等于 !=

不等于 ^=

不等于 <>

--------------------- 

模糊查询like

( _代表一个字符，%代表所有字符)

SQL> select OBJECT_NAME,owner from t where owner like '___TT';

SQL> select * from t where owner like '%TT%';

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

is null（空）   is not null （非空）

SQL> select * from t where owner is null;

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

SQL> select * from t where OBJECT_ID between 51070 and 51080;

（OBJECT_ID值在10000到20000之间）

--------------------------vfast_jiaoxue_database_10

where 子查询

SQL> select * from t where owner =(select owner from t where OBJECT_ID=51079);

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

组合表

 create table t1 (id int,xingming varchar2(10));

insert into t1 values(1,'zs');

insert into t1 values(2,'ls');

insert into t1 values(3,'ww');

SQL> commit;

create table t2 (id int,gongzi int);

insert into t2 values(1,10000);

insert into t2 values(2,20000);

commit;

SQL> select T1.xingming,T2.gongzi from t1,t2 where T1.id=T2.id;

    

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

创建视图

SQL> create view v_t2

    as select * from t2 where gongzi<=10000;

SQL> select * from v_t2;

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

oracle 串函数  ************

|| 连接符

SQL> select id||'        '||xingming from t1;

LTRIM,RTRIM,TRIM

LTRIM:左删除

RTRIM:右删除

TRIM:删除串两边的字符

SQL> select RTRIM(gongzi,'0') from t2;

SQL> select rtrim(' aaa ') from dual;

（发现aaa的右面空格没有了）

SQL> select trim(' aaa ') from dual;

(发现aaa两端的空格没了)

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

length求得是字符长度

SQL> select length('haha.hehe') from dual;

lengthb求得是字节长度(如有中文时使用)

SQL> select lengthb('haha.hehe') from dual;

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

TO_CHAR 是把日期或数字转换为字符串 ********************

SQL> select to_char(123,'9999.00') from dual 

SQL> select to_char(123,'$99,999.99') from dual;

查看时间

SQL> select sysdate from dual;

SQL> select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual;

SQL> create table t12 (id int,t date);  

SQL>  insert into t12 values(1,to_date('2012-12-12 12:12:12','yyyy-mm-dd hh24:mi:ss'));

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

substr 截取函数  ********************

SQL> select substr('abcdef',2,3) from dual;

(截取从第二个字符开始的3个字符)

SQL> select substr('abcdef',-5) from dual;

(截取后5位)

to_char(sj,'yyyy-mm-dd')  t3    sj index

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

语法:

instr(string,substring,position,occurrence)

string:代表源字符串

substring:代表想从源字符串中查找的子串

position:代表查找开始的位置,默认为1

occurrence:代表查找值弟几次出现,结果为字符串的位置

SQL> select instr('hello word','o',-1,1) from dual;

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

ascii函数将字符转换成其对应的ascii码，而chr函数将数字转换成对应acscii码的字符

SQL> select ascii('a') from dual;

SQL> select chr(97) from dual;

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

四个字符组成的代码 (SOUNDEX) 以评估两个字符串的相似性

SQL> select soundex('two'),soundex('too'),soundex('to') from dual;

SQL> select soundex('abc'),soundex('cba') from dual;

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

聚集函数  *************************

avg(平均值)

SQL> select avg(gongzi) from t2;

sum(求和)

SQL> select sum(gongzi) from t2;

min(最小值)

SQL> select min(gongzi) from t2;

max(最大值)

SQL> select max(gongzi) from t2;

count(行计数)

SQL> select count(*) from t2; 

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

nvl(返回一个非空值) ******************

nvl(e1,e2)功能为: 如果e1值为空,结果就显示为 e2设置的值

SQL>  select nvl(name,0) from aa;

NVL2(E1, E2, E3)的功能为：如果E1为NULL，则函数返回E3，若E1不为null，则返回E2

SQL> select nvl2(name,1,0) from aa;

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

abs ceil 返回绝对值 

SQL> select abs(-5) from dual; (返回值为5)

SQL> select abs(5.5)  from dual;(返回值为5.5)

SQL> select ceil(5.4) from dual;(返回值为6)

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

vm_concat合并列

SQL> select * from tt;

      BMID NAME               GZ

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

         1 zs              10000

         1 ls              12000

         1 ww              15000

         2 haha            30000

         3 hehe            50000

显示每部门人名

SQL> select id,wm_concat(xingming) from t5 group by id;

显示每部门人名和工资

SQL> select id,wm_concat(xingming||'('||gongzi||')') from t5 group by id;

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

sqrt 求平方根

SQL> select sqrt(64) from dual;

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

LPAD

lpad函数将左边的字符串填充一些特定的字符，其语法格式如下： lpad( String, 截取长度, 填充字符串 ) 如果截取长度比原字符串的长度要短，lpad函数将会把字符串截取成截取长度; 填充字符串是要添加到String的左边，如果这个参数未写，lpad函数将会在string1的左边补齐空格。

 例如： lpad('tech', 7); 将返回' tech'

lpad('tech', 2); 将返回'te'

lpad('tech', 8, '0'); 将返回'0000tech'

lpad('tech on the net', 15, 'z'); 将返回 'tech on the net'

lpad('tech on the net', 16, 'z'); 将返回 'ztech on the net'

Lpad（str1,number,str2），这个函数的意思是，如果str1不足number那么多位，则使用str2去补齐左边的空

SELECT lpad('!!',5,'aaaa') FROM dual

--结果

aaa!!

 

rpad函数与lpad函数正好相反，rpad函数将左边的字符串填充一些特定的字符，其语法格式如下： rpad( String, 截取长度, 填充字符串 )

SELECT rpad('!!',5,'aaaa') FROM dual

--结果

!!aaa

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

Round 函数 (四舍五入) ********************

SQL> select round(123.123) from dual;

SQL> select round(123.8) from dual;

trunc 截掉小数点后值

SQL> select trunc(123.8) from dual;

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

sign取数字n的符号,大于0返回1,小于0返回-1,等于0返回0

SQL> select sign(100),sign(-100),sign(0) from dual;

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

删除重复行  ******************

SQL> select distinct(xingming) from t11;

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

时间格式

SQL> select to_char(CREATED,'yyyy-mm-dd hh24:mi:ss') from t where rownum<10;

SQL> create table tt2(id int,time date);

SQL> insert into tt2 values (1,to_date('2011-11-11 11:11:11' 'YYYY-MM-DD HH24:MI:SS'));

SQL> select to_char(TIME,'YYYY-MM-DD HH24:MI:SS') from tt2;

本文出自 “linux” 博客，谢绝转载！