关于SQL函数 ||instr()to_char()to_date()substr()trunc()... 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 38.MONTHS_BETWEEN(date2,date1)给出date2-date1的月份SQL> select months_between('19-12月-1999','19-3月-1999') mon_between from dual;MON_BETWEEN-----------9SQL>selectmonths_between(to_date('2000.05.20','yyyy.mm.dd'),to_date('2005.05.20','yyyy.mm.dd')) mon_betw from dual;MON_BETW----------6039.NEW_TIME(date,'this','that')给出在this时区=other时区的日期和时间SQL> select to_char(sysdate,'yyyy.mm.dd hh24:mi:ss') bj_time,to_char(new_time2 (sysdate,'PDT','GMT'),'yyyy.mm.dd hh24:mi:ss') los_angles from dual;BJ_TIME LOS_ANGLES------------------- -------------------2004.05.09 11:05:32 2004.05.09 18:05:3240.NEXT_DAY(date,'day')给出日期date和星期x之后计算下一个星期的日期SQL> select next_day('18-5月-2001','星期五') next_day from dual;NEXT_DAY----------25-5月 -01 41.SYSDATE用来得到系统的当前日期SQL> select to_char(sysdate,'dd-mm-yyyy day') from dual;TO_CHAR(SYSDATE,'-----------------09-05-2004 星期日trunc(date,fmt)按照给出的要求将日期截断,如果fmt='mi'表示保留分,截断秒SQL> select to_char(trunc(sysdate,'hh'),'yyyy.mm.dd hh24:mi:ss') hh,2 to_char(trunc(sysdate,'mi'),'yyyy.mm.dd hh24:mi:ss') hhmm from dual;HH HHMM------------------- -------------------2004.05.09 11:00:00 2004.05.09 11:17:00 42.CHARTOROWID将字符数据类型转换为ROWID类型SQL> select rowid,rowidtochar(rowid),ename from scott.emp;ROWID ROWIDTOCHAR(ROWID) ENAME------------------ ------------------ ----------AAAAfKAACAAAAEqAAA AAAAfKAACAAAAEqAAA SMITHAAAAfKAACAAAAEqAAB AAAAfKAACAAAAEqAAB ALLENAAAAfKAACAAAAEqAAC AAAAfKAACAAAAEqAAC WARDAAAAfKAACAAAAEqAAD AAAAfKAACAAAAEqAAD JONES43.CONVERT(c,dset,sset)将源字符串 sset从一个语言字符集转换到另一个目的dset字符集SQL> select convert('strutz','we8hp','f7dec') "conversion" from dual;conver------strutz44.HEXTORAW将一个十六进制构成的字符串转换为二进制45.RAWTOHEXT将一个二进制构成的字符串转换为十六进制 46.ROWIDTOCHAR将ROWID数据类型转换为字符类型 47.TO_CHAR(date,'format')SQL> select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') from dual;TO_CHAR(SYSDATE,'YY-------------------2004/05/09 21:14:41 48.TO_DATE(string,'format')将字符串转化为ORACLE中的一个日期49.TO_MULTI_BYTE将字符串中的单字节字符转化为多字节字符SQL> select to_multi_byte('高') from dual;TO--高50.TO_NUMBER将给出的字符转换为数字SQL> select to_number('1999') year from dual;YEAR---------199951.BFILENAME(dir,file)指定一个外部二进制文件SQL>insert into file_tb1 values(bfilename('lob_dir1','image1.gif'));52.CONVERT('x','desc','source')将x字段或变量的源source转换为descSQL> select sid,serial#,username,decode(command,2 0,'none',3 2,'insert',4 3,5 'select',6 6,'update',7 7,'delete',8 8,'drop',9 'other') cmd from v$session where type!='background';SID SERIAL# USERNAME CMD--------- --------- ------------------------------ ------1 1 none2 1 none3 1 none4 1 none5 1 none6 1 none7 1275 none8 1275 none9 20 GAO select10 40 GAO none53.DUMP(s,fmt,start,length)DUMP函数以fmt指定的内部数字格式返回一个VARCHAR2类型的值SQL> col global_name for a30SQL> col dump_string for a50SQL> set lin 200SQL> select global_name,dump(global_name,1017,8,5) dump_string from global_name;GLOBAL_NAME DUMP_STRING------------------------------ --------------------------------------------------ORACLE.WORLD Typ=1 Len=12 CharacterSet=ZHS16GBK: W,O,R,L,D54.EMPTY_BLOB()和EMPTY_CLOB()这两个函数都是用来对大数据类型字段进行初始化操作的函数55.GREATEST返回一组表达式中的最大值,即比较字符的编码大小.SQL> select greatest('AA','AB','AC') from dual;GR--ACSQL> select greatest('啊','安','天') from dual;GR--天56.LEAST返回一组表达式中的最小值 SQL> select least('啊','安','天') from dual;LE--啊57.UID返回标识当前用户的唯一整数SQL> show userUSER 为"GAO"SQL> select username,user_id from dba_users where user_id=uid;USERNAME USER_ID------------------------------ ---------GAO 25 58.USER返回当前用户的名字SQL> select user from dual;USER------------------------------GAO59.USEREVN返回当前用户环境的信息,opt可以是:ENTRYID,SESSIONID,TERMINAL,ISDBA,LABLE,LANGUAGE,CLIENT_INFO,LANG,VSIZEISDBA 查看当前用户是否是DBA如果是则返回trueSQL> select userenv('isdba') from dual;USEREN------FALSESQL> select userenv('isdba') from dual;USEREN------TRUESESSION返回会话标志SQL> select userenv('sessionid') from dual;USERENV('SESSIONID')--------------------152ENTRYID返回会话人口标志SQL> select userenv('entryid') from dual;USERENV('ENTRYID')------------------0INSTANCE返回当前INSTANCE的标志SQL> select userenv('instance') from dual;USERENV('INSTANCE')-------------------1LANGUAGE返回当前环境变量SQL> select userenv('language') from dual;USERENV('LANGUAGE')----------------------------------------------------SIMPLIFIED CHINESE_CHINA.ZHS16GBKLANG返回当前环境的语言的缩写SQL> select userenv('lang') from dual;USERENV('LANG')----------------------------------------------------ZHSTERMINAL返回用户的终端或机器的标志SQL> select userenv('terminal') from dual;USERENV('TERMINA----------------GAOVSIZE(X)返回X的大小(字节)数SQL> select vsize(user),user from dual;VSIZE(USER) USER----------- ------------------------------6 SYSTEM 60.AVG(DISTINCT|ALL)all表示对所有的值求平均值,distinct只对不同的值求平均值SQLWKS> create table table3(xm varchar(8),sal number(7,2));语句已处理。SQLWKS> insert into table3 values('gao',1111.11);SQLWKS> insert into table3 values('gao',1111.11);SQLWKS> insert into table3 values('zhu',5555.55);SQLWKS> commit;SQL> select avg(distinct sal) from gao.table3;AVG(DISTINCTSAL)----------------3333.33SQL> select avg(all sal) from gao.table3;AVG(ALLSAL)-----------2592.5961.MAX(DISTINCT|ALL)求最大值,ALL表示对所有的值求最大值,DISTINCT表示对不同的值求最大值,相同的只取一次SQL> select max(distinct sal) from scott.emp;MAX(DISTINCTSAL)----------------500062.MIN(DISTINCT|ALL)求最小值,ALL表示对所有的值求最小值,DISTINCT表示对不同的值求最小值,相同的只取一次SQL> select min(all sal) from gao.table3;MIN(ALLSAL)-----------1111.1163.STDDEV(distinct|all)求标准差,ALL表示对所有的值求标准差,DISTINCT表示只对不同的值求标准差SQL> select stddev(sal) from scott.emp;STDDEV(SAL)-----------1182.5032SQL> select stddev(distinct sal) from scott.emp;STDDEV(DISTINCTSAL)-------------------1229.951 64.VARIANCE(DISTINCT|ALL)求协方差 SQL> select variance(sal) from scott.emp;VARIANCE(SAL)-------------1398313.965.GROUP BY主要用来对一组数进行统计SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno;DEPTNO COUNT(*) SUM(SAL)--------- --------- ---------10 3 875020 5 1087530 6 9400 66.HAVING对分组统计再加限制条件SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno having count(*)>=5;DEPTNO COUNT(*) SUM(SAL)--------- --------- ---------20 5 1087530 6 9400SQL> select deptno,count(*),sum(sal) from scott.emp having count(*)>=5 group by deptno ;DEPTNO COUNT(*) SUM(SAL)--------- --------- ---------20 5 1087530 6 940067.ORDER BY用于对查询到的结果进行排序输出SQL> select deptno,ename,sal from scott.emp order by deptno,sal desc;DEPTNO ENAME SAL--------- ---------- ---------10 KING 500010 CLARK 245010 MILLER 130020 SCOTT 300020 FORD 300020 JONES 297520 ADAMS 110020 SMITH 80030 BLAKE 285030 ALLEN 160030 TURNER 150030 WARD 125030 MARTIN 125030 JAMES 950 要看你是处理什么样的问题多一点,很常用的就是转换函数,有关string的函数,数学函数,几个特殊的函数 SQL函数巨多 ??? 100来个吧 下个帮助文档来看看我看比其他语言的少多了 查找并替换 多音字 初始数据的问题 ★☆★☆★☆★☆十万火急,请高手们救我!!! Oracle连接奇怪的问题 求助关联两表之间的"嵌套"统计,如何提高效率. merge into不能用在存储过程里吗? subtype怎么用,是不是可以来定义一个新类型保存到数据库后,可以用这类型建我的业务表? 如何把ORACLE734的DMP导入到ORACLE805中? 如何使Oracle 9i在开始时不自动启动?? 单表横表转纵表查询速度慢求解决方法? Oracle里能创建Group Function吗? Oracle存储过程中 Ref cursor 问题
给出date2-date1的月份
SQL> select months_between('19-12月-1999','19-3月-1999') mon_between from dual;MON_BETWEEN
-----------
9
SQL>selectmonths_between(to_date('2000.05.20','yyyy.mm.dd'),to_date('2005.05.20','yyyy.mm.dd')) mon_betw from dual;MON_BETW
---------
-60
39.NEW_TIME(date,'this','that')
给出在this时区=other时区的日期和时间
SQL> select to_char(sysdate,'yyyy.mm.dd hh24:mi:ss') bj_time,to_char(new_time
2 (sysdate,'PDT','GMT'),'yyyy.mm.dd hh24:mi:ss') los_angles from dual;BJ_TIME LOS_ANGLES
------------------- -------------------
2004.05.09 11:05:32 2004.05.09 18:05:32
40.NEXT_DAY(date,'day')
给出日期date和星期x之后计算下一个星期的日期
SQL> select next_day('18-5月-2001','星期五') next_day from dual;NEXT_DAY
----------
25-5月 -01 41.SYSDATE
用来得到系统的当前日期
SQL> select to_char(sysdate,'dd-mm-yyyy day') from dual;TO_CHAR(SYSDATE,'
-----------------
09-05-2004 星期日
trunc(date,fmt)按照给出的要求将日期截断,如果fmt='mi'表示保留分,截断秒
SQL> select to_char(trunc(sysdate,'hh'),'yyyy.mm.dd hh24:mi:ss') hh,
2 to_char(trunc(sysdate,'mi'),'yyyy.mm.dd hh24:mi:ss') hhmm from dual;HH HHMM
------------------- -------------------
2004.05.09 11:00:00 2004.05.09 11:17:00 42.CHARTOROWID
将字符数据类型转换为ROWID类型
SQL> select rowid,rowidtochar(rowid),ename from scott.emp;ROWID ROWIDTOCHAR(ROWID) ENAME
------------------ ------------------ ----------
AAAAfKAACAAAAEqAAA AAAAfKAACAAAAEqAAA SMITH
AAAAfKAACAAAAEqAAB AAAAfKAACAAAAEqAAB ALLEN
AAAAfKAACAAAAEqAAC AAAAfKAACAAAAEqAAC WARD
AAAAfKAACAAAAEqAAD AAAAfKAACAAAAEqAAD JONES
43.CONVERT(c,dset,sset)
将源字符串 sset从一个语言字符集转换到另一个目的dset字符集
SQL> select convert('strutz','we8hp','f7dec') "conversion" from dual;conver
------
strutz
44.HEXTORAW
将一个十六进制构成的字符串转换为二进制
45.RAWTOHEXT
将一个二进制构成的字符串转换为十六进制 46.ROWIDTOCHAR
将ROWID数据类型转换为字符类型 47.TO_CHAR(date,'format')
SQL> select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') from dual;TO_CHAR(SYSDATE,'YY
-------------------
2004/05/09 21:14:41 48.TO_DATE(string,'format')
将字符串转化为ORACLE中的一个日期
49.TO_MULTI_BYTE
将字符串中的单字节字符转化为多字节字符
SQL> select to_multi_byte('高') from dual;TO
--
高
50.TO_NUMBER
将给出的字符转换为数字
SQL> select to_number('1999') year from dual;YEAR
---------
1999
51.BFILENAME(dir,file)
指定一个外部二进制文件
SQL>insert into file_tb1 values(bfilename('lob_dir1','image1.gif'));
52.CONVERT('x','desc','source')
将x字段或变量的源source转换为desc
SQL> select sid,serial#,username,decode(command,
2 0,'none',
3 2,'insert',
4 3,
5 'select',
6 6,'update',
7 7,'delete',
8 8,'drop',
9 'other') cmd from v$session where type!='background';SID SERIAL# USERNAME CMD
--------- --------- ------------------------------ ------
1 1 none
2 1 none
3 1 none
4 1 none
5 1 none
6 1 none
7 1275 none
8 1275 none
9 20 GAO select
10 40 GAO none
53.DUMP(s,fmt,start,length)
DUMP函数以fmt指定的内部数字格式返回一个VARCHAR2类型的值
SQL> col global_name for a30
SQL> col dump_string for a50
SQL> set lin 200
SQL> select global_name,dump(global_name,1017,8,5) dump_string from global_name;GLOBAL_NAME DUMP_STRING
------------------------------ --------------------------------------------------
ORACLE.WORLD Typ=1 Len=12 CharacterSet=ZHS16GBK: W,O,R,L,D
54.EMPTY_BLOB()和EMPTY_CLOB()
这两个函数都是用来对大数据类型字段进行初始化操作的函数
55.GREATEST
返回一组表达式中的最大值,即比较字符的编码大小.
SQL> select greatest('AA','AB','AC') from dual;GR
--
AC
SQL> select greatest('啊','安','天') from dual;GR
--
天
56.LEAST
返回一组表达式中的最小值
SQL> select least('啊','安','天') from dual;LE
--
啊
57.UID
返回标识当前用户的唯一整数
SQL> show user
USER 为"GAO"
SQL> select username,user_id from dba_users where user_id=uid;USERNAME USER_ID
------------------------------ ---------
GAO 25 58.USER
返回当前用户的名字
SQL> select user from dual;USER
------------------------------
GAO
59.USEREVN
返回当前用户环境的信息,opt可以是:
ENTRYID,SESSIONID,TERMINAL,ISDBA,LABLE,LANGUAGE,CLIENT_INFO,LANG,VSIZE
ISDBA 查看当前用户是否是DBA如果是则返回true
SQL> select userenv('isdba') from dual;USEREN
------
FALSE
SQL> select userenv('isdba') from dual;USEREN
------
TRUE
SESSION
返回会话标志
SQL> select userenv('sessionid') from dual;USERENV('SESSIONID')
--------------------
152
ENTRYID
返回会话人口标志
SQL> select userenv('entryid') from dual;USERENV('ENTRYID')
------------------
0
INSTANCE
返回当前INSTANCE的标志
SQL> select userenv('instance') from dual;USERENV('INSTANCE')
-------------------
1
LANGUAGE
返回当前环境变量
SQL> select userenv('language') from dual;USERENV('LANGUAGE')
----------------------------------------------------
SIMPLIFIED CHINESE_CHINA.ZHS16GBK
LANG
返回当前环境的语言的缩写
SQL> select userenv('lang') from dual;USERENV('LANG')
----------------------------------------------------
ZHS
TERMINAL
返回用户的终端或机器的标志
SQL> select userenv('terminal') from dual;USERENV('TERMINA
----------------
GAO
VSIZE(X)
返回X的大小(字节)数
SQL> select vsize(user),user from dual;VSIZE(USER) USER
----------- ------------------------------
6 SYSTEM 60.AVG(DISTINCT|ALL)
all表示对所有的值求平均值,distinct只对不同的值求平均值
SQLWKS> create table table3(xm varchar(8),sal number(7,2));
语句已处理。
SQLWKS> insert into table3 values('gao',1111.11);
SQLWKS> insert into table3 values('gao',1111.11);
SQLWKS> insert into table3 values('zhu',5555.55);
SQLWKS> commit;SQL> select avg(distinct sal) from gao.table3;AVG(DISTINCTSAL)
----------------
3333.33SQL> select avg(all sal) from gao.table3;AVG(ALLSAL)
-----------
2592.59
61.MAX(DISTINCT|ALL)
求最大值,ALL表示对所有的值求最大值,DISTINCT表示对不同的值求最大值,相同的只取一次
SQL> select max(distinct sal) from scott.emp;MAX(DISTINCTSAL)
----------------
5000
62.MIN(DISTINCT|ALL)
求最小值,ALL表示对所有的值求最小值,DISTINCT表示对不同的值求最小值,相同的只取一次
SQL> select min(all sal) from gao.table3;MIN(ALLSAL)
-----------
1111.11
63.STDDEV(distinct|all)
求标准差,ALL表示对所有的值求标准差,DISTINCT表示只对不同的值求标准差
SQL> select stddev(sal) from scott.emp;STDDEV(SAL)
-----------
1182.5032SQL> select stddev(distinct sal) from scott.emp;STDDEV(DISTINCTSAL)
-------------------
1229.951 64.VARIANCE(DISTINCT|ALL)
求协方差 SQL> select variance(sal) from scott.emp;VARIANCE(SAL)
-------------
1398313.9
65.GROUP BY
主要用来对一组数进行统计
SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno;DEPTNO COUNT(*) SUM(SAL)
--------- --------- ---------
10 3 8750
20 5 10875
30 6 9400 66.HAVING
对分组统计再加限制条件
SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno having count(*)>=5;DEPTNO COUNT(*) SUM(SAL)
--------- --------- ---------
20 5 10875
30 6 9400
SQL> select deptno,count(*),sum(sal) from scott.emp having count(*)>=5 group by deptno ;DEPTNO COUNT(*) SUM(SAL)
--------- --------- ---------
20 5 10875
30 6 9400
67.ORDER BY
用于对查询到的结果进行排序输出
SQL> select deptno,ename,sal from scott.emp order by deptno,sal desc;DEPTNO ENAME SAL
--------- ---------- ---------
10 KING 5000
10 CLARK 2450
10 MILLER 1300
20 SCOTT 3000
20 FORD 3000
20 JONES 2975
20 ADAMS 1100
20 SMITH 800
30 BLAKE 2850
30 ALLEN 1600
30 TURNER 1500
30 WARD 1250
30 MARTIN 1250
30 JAMES 950
100来个吧 下个帮助文档来看看
我看比其他语言的少多了