数据库基础函数
SQL中的單記錄函數(shù)
- 補充
NVL(EXP1, EXP2)
如果 EXP1 為空，則返回 EXP2 , 否則返回 EXP1
例如 : SELECT NVL('', 'A' ) FROM DUAL ;
返回結(jié)果 : A
NVL2(EXP1, EXP2, EXP3)
如果 exp1 為空，則返回 exp3, 否則返回 exp2 .
例如 : SELECT NVL2('','A' ,'B' ) FROM DUAL;
返回結(jié)果 : B
NULLIF(EXP1,EXP2)
如果 exp1=exp2, 則返回空，否則返回 exp1
例如 : SELECT NULLIF('A','') FROM DUAL;
返回結(jié)果 : A
例如 : SELECT NULLIF('','') FROM DUAL;??-- 如果兩個null 進行比較
返回結(jié)果 : 空
1.ASCII?
返回與指定的字符對應(yīng)的十進制數(shù);?
SQL> select ascii('A') A,ascii('a') a,ascii('0') zero,ascii(' ') space from dual;
??????? A???????? A????? ZERO???? SPACE?
--------- --------- --------- ---------?
?????? 65??????? 97??????? 48??????? 32
2.CHR?
給出整數(shù),返回對應(yīng)的字符;?
SQL> select chr(54740) zhao,chr(65) chr65 from dual;
ZH C?
-- -?
趙 A
3.CONCAT?
連接兩個字符串;?
SQL> select concat('010-','88888888')||'轉(zhuǎn)23'? 高乾競電話 from dual;
高乾競電話?
----------------?
010-88888888轉(zhuǎn)23
4.INITCAP?
返回字符串并將字符串的第一個字母變?yōu)榇髮??
SQL> select initcap('smith') upp from dual;
UPP?
-----?
Smith
5.INSTR(C1,C2,I,J)?
在一個字符串中搜索指定的字符,返回發(fā)現(xiàn)指定的字符的位置;?
C1??? 被搜索的字符串?
C2??? 希望搜索的字符串?
I???? 搜索的開始位置,默認為1?
J???? 出現(xiàn)的位置,默認為1( 即第幾次出現(xiàn)1,帶表第一次出現(xiàn)，2代表第2次出現(xiàn)，以下例子如果是1，則返回的結(jié)果應(yīng)該是2，因為前邊還有個符合的 ra 就是在 oracle這個字符串中 )?
SQL> select instr('oracle traning','ra',1,2) instring from dual;
INSTRING?
---------?
??????? 9
6.LENGTH?
返回字符串的長度;?
SQL> select name,length(name),addr,length(addr),sal,length(to_char(sal)) from gao.nchar_tst;
NAME?? LENGTH(NAME) ADDR???????????? LENGTH(ADDR)?????? SAL LENGTH(TO_CHAR(SAL))?
------ ------------ ---------------- ------------ --------- --------------------?
高乾競??????????? 3 北京市海錠區(qū)??????????????? 6?? 9999.99??????????????????? 7
7.LOWER?
返回字符串,并將所有的字符小寫?
SQL> select lower('AaBbCcDd')AaBbCcDd from dual;
AABBCCDD?
--------?
aabbccdd
8.UPPER?
返回字符串,并將所有的字符大寫?
SQL> select upper('AaBbCcDd') upper from dual;
UPPER?
--------?
AABBCCDD
9.RPAD和LPAD(粘貼字符)?
RPAD? 在列的右邊粘貼字符?
LPAD? 在列的左邊粘貼字符?
SQL> select lpad(rpad('gao',10,'*'),17,'*')from dual;
LPAD(RPAD('GAO',1?
-----------------?
*******gao*******?
不夠字符則用*來填滿
10.LTRIM和RTRIM?
LTRIM? 刪除左邊出現(xiàn)的字符串?
RTRIM? 刪除右邊出現(xiàn)的字符串?
SQL> select ltrim(rtrim('?? gao qian jing?? ',' '),' ') from dual;
LTRIM(RTRIM('?
-------------?
gao qian jing
11.SUBSTR(string,start,count)?
取子字符串,從start開始,取count個?
SQL> select substr('13088888888',3,8) from dual;
SUBSTR('?
--------?
08888888
12.REPLACE('string','s1','s2')?
string?? 希望被替換的字符或變量?
s1?????? 被替換的字符串?
s2?????? 要替換的字符串?
SQL> select replace('he love you','he','i') from dual;
REPLACE('H?
----------?
i love you
13.SOUNDEX?
返回一個與給定的字符串讀音相同的字符串?
SQL> create table table1(xm varchar(8));?
SQL> insert into table1 values('weather');?
SQL> insert into table1 values('wether');?
SQL> insert into table1 values('gao');
SQL> select xm from table1 where soundex(xm)=soundex('weather');
XM?
--------?
weather?
wether
14.TRIM('s' from 'string')?
LEADING?? 剪掉前面的字符?
TRAILING? 剪掉后面的字符?
如果不指定,默認為空格符
15.ABS?
返回指定值的絕對值?
SQL> select abs(100),abs(-100) from dual;
ABS(100) ABS(-100)?
--------- ---------?
????? 100?????? 100
16.ACOS?
給出反余弦的值?
SQL> select acos(-1) from dual;
ACOS(-1)?
---------?
3.1415927
17.ASIN?
給出反正弦的值?
SQL> select asin(0.5) from dual;
ASIN(0.5)?
---------?
.52359878
18.ATAN?
返回一個數(shù)字的反正切值?
SQL> select atan(1) from dual;
? ATAN(1)?
---------?
.78539816
19.CEIL?
返回大于或等于給出數(shù)字的最小整數(shù)?
SQL> select ceil(3.1415927) from dual;
CEIL(3.1415927)?
---------------?
????????????? 4
20.COS?
返回一個給定數(shù)字的余弦?
SQL> select cos(-3.1415927) from dual;
COS(-3.1415927)?
---------------?
???????????? -1
21.COSH?
返回一個數(shù)字反余弦值?
SQL> select cosh(20) from dual;
COSH(20)?
---------?
242582598
22.EXP?
返回一個數(shù)字e的n次方根?
SQL> select exp(2),exp(1) from dual;
?? EXP(2)??? EXP(1)?
--------- ---------?
7.3890561 2.7182818
23.FLOOR?
對給定的數(shù)字取整數(shù)?
SQL> select floor(2345.67) from dual;
FLOOR(2345.67)?
--------------?
????????? 2345
24.LN?
返回一個數(shù)字的對數(shù)值?
SQL> select ln(1),ln(2),ln(2.7182818) from dual;
??? LN(1)???? LN(2) LN(2.7182818)?
--------- --------- -------------?
??????? 0 .69314718???? .99999999
25.LOG(n1,n2)?
返回一個以n1為底n2的對數(shù)?
SQL> select log(2,1),log(2,4) from dual;
LOG(2,1)? LOG(2,4)?
--------- ---------?
??????? 0???????? 2
26.MOD(n1,n2)?
返回一個n1除以n2的余數(shù)?
SQL> select mod(10,3),mod(3,3),mod(2,3) from dual;
MOD(10,3)? MOD(3,3)? MOD(2,3)?
--------- --------- ---------?
??????? 1???????? 0???????? 2
27.POWER?
返回n1的n2次方根?
SQL> select power(2,10),power(3,3) from dual;
POWER(2,10) POWER(3,3)?
----------- ----------?
?????? 1024???????? 27
28.ROUND和TRUNC?
按照指定的精度進行舍入?
SQL> select round(55.5),round(-55.4),trunc(55.5),trunc(-55.5) from dual;
ROUND(55.5) ROUND(-55.4) TRUNC(55.5) TRUNC(-55.5)?
----------- ------------ ----------- ------------?
???????? 56????????? -55????????? 55????????? -55
29.SIGN?
取數(shù)字n的符號,大于0返回1,小于0返回-1,等于0返回0?
SQL> select sign(123),sign(-100),sign(0) from dual;
SIGN(123) SIGN(-100)?? SIGN(0)?
--------- ---------- ---------?
??????? 1???????? -1???????? 0
30.SIN?
返回一個數(shù)字的正弦值?
SQL> select sin(1.57079) from dual;
SIN(1.57079)?
------------?
?????????? 1
31.SIGH?
返回雙曲正弦的值?
SQL> select sin(20),sinh(20) from dual;
? SIN(20)? SINH(20)?
--------- ---------?
.91294525 242582598
32.SQRT?
返回數(shù)字n的根?
SQL> select sqrt(64),sqrt(10) from dual;
SQRT(64)? SQRT(10)?
--------- ---------?
??????? 8 3.1622777
33.TAN?
返回數(shù)字的正切值?
SQL> select tan(20),tan(10) from dual;
? TAN(20)?? TAN(10)?
--------- ---------?
2.2371609 .64836083
34.TANH?
返回數(shù)字n的雙曲正切值?
SQL> select tanh(20),tan(20) from dual;
TANH(20)?? TAN(20)?
--------- ---------?
??????? 1 2.2371609
35.TRUNC?
按照指定的精度截取一個數(shù)?
SQL> select trunc(124.1666,-2) trunc1,trunc(124.16666,2) from dual;
?? TRUNC1 TRUNC(124.16666,2)?
--------- ------------------?
????? 100???????????? 124.16
36.ADD_MONTHS?
增加或減去月份?
SQL> select to_char(add_months(to_date('199912','yyyymm'),2),'yyyymm') from dual;
TO_CHA?
------?
200002?
SQL> select to_char(add_months(to_date('199912','yyyymm'),-2),'yyyymm') from dual;
TO_CHA?
------?
199910
37.LAST_DAY?
返回日期的最后一天?
SQL> select to_char(sysdate,'yyyy.mm.dd'),to_char((sysdate)+1,'yyyy.mm.dd') from dual;
TO_CHAR(SY TO_CHAR((S?
---------- ----------?
2004.05.09 2004.05.10?
SQL> select last_day(sysdate) from dual;
LAST_DAY(S?
----------?
31-5月 -04
38.MONTHS_BETWEEN(date2,date1)?
給出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')?
給出在this時區(qū)=other時區(qū)的日期和時間?
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')?
給出日期date和星期x之后計算下一個星期的日期?
SQL> select next_day('18-5月-2001','星期五') next_day from dual;
NEXT_DAY?
----------?
25-5月 -01
41.SYSDATE?
用來得到系統(tǒng)的當前日期?
SQL> select to_char(sysdate,'dd-mm-yyyy day') from dual;
TO_CHAR(SYSDATE,'?
-----------------?
09-05-2004 星期日?
trunc(date,fmt)按照給出的要求將日期截斷,如果fmt='mi'表示保留分,截斷秒?
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?
將字符數(shù)據(jù)類型轉(zhuǎn)換為ROWID類型?
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)?
將源字符串 sset從一個語言字符集轉(zhuǎn)換到另一個目的dset字符集?
SQL> select convert('strutz','we8hp','f7dec') "conversion" from dual;
conver?
------?
strutz
44.HEXTORAW?
將一個十六進制構(gòu)成的字符串轉(zhuǎn)換為二進制
45.RAWTOHEXT?
將一個二進制構(gòu)成的字符串轉(zhuǎn)換為十六進制
46.ROWIDTOCHAR?
將ROWID數(shù)據(jù)類型轉(zhuǎn)換為字符類型
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')?
將字符串轉(zhuǎn)化為ORACLE中的一個日期
49.TO_MULTI_BYTE?
將字符串中的單字節(jié)字符轉(zhuǎn)化為多字節(jié)字符?
SQL>? select to_multi_byte('高') from dual;
TO?
--?
高
50.TO_NUMBER?
將給出的字符轉(zhuǎn)換為數(shù)字?
SQL> select to_number('1999') year from dual;
???? YEAR?
---------?
???? 1999
51.BFILENAME(dir,file)?
指定一個外部二進制文件?
SQL>insert into file_tb1 values(bfilename('lob_dir1','image1.gif'));
52.CONVERT('x','desc','source')?
將x字段或變量的源source轉(zhuǎn)換為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函數(shù)以fmt指定的內(nèi)部數(shù)字格式返回一個VARCHAR2類型的值?
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()?
這兩個函數(shù)都是用來對大數(shù)據(jù)類型字段進行初始化操作的函數(shù)
55.GREATEST?
返回一組表達式中的最大值,即比較字符的編碼大小.?
SQL> select greatest('AA','AB','AC') from dual;
GR?
--?
AC?
SQL> select greatest('啊','安','天') from dual;
GR?
--?
天
56.LEAST?
返回一組表達式中的最小值?
SQL> select least('啊','安','天') from dual;
LE?
--?
啊
57.UID?
返回標識當前用戶的唯一整數(shù)?
SQL> show user?
USER 為"GAO"?
SQL> select username,user_id from dba_users where user_id=uid;
USERNAME???????????????????????? USER_ID?
------------------------------ ---------?
GAO?????????????????????????????????? 25
58.USER?
返回當前用戶的名字?
SQL> select user from? dual;
USER?
------------------------------?
GAO
59.USEREVN?
返回當前用戶環(huán)境的信息,opt可以是:?
ENTRYID,SESSIONID,TERMINAL,ISDBA,LABLE,LANGUAGE,CLIENT_INFO,LANG,VSIZE?
ISDBA? 查看當前用戶是否是DBA如果是則返回true?
SQL> select userenv('isdba') from dual;
USEREN?
------?
FALSE?
SQL> select userenv('isdba') from dual;
USEREN?
------?
TRUE?
SESSION?
返回會話標志?
SQL> select userenv('sessionid') from dual;
USERENV('SESSIONID')?
--------------------?
???????????????? 152?
ENTRYID?
返回會話人口標志?
SQL> select userenv('entryid') from dual;
USERENV('ENTRYID')?
------------------?
???????????????? 0?
INSTANCE?
返回當前INSTANCE的標志?
SQL> select userenv('instance') from dual;
USERENV('INSTANCE')?
-------------------?
????????????????? 1?
LANGUAGE?
返回當前環(huán)境變量?
SQL> select userenv('language') from dual;
USERENV('LANGUAGE')?
----------------------------------------------------?
SIMPLIFIED CHINESE_CHINA.ZHS16GBK?
LANG?
返回當前環(huán)境的語言的縮寫?
SQL> select userenv('lang') from dual;
USERENV('LANG')?
----------------------------------------------------?
ZHS?
TERMINAL?
返回用戶的終端或機器的標志?
SQL> select userenv('terminal') from dual;
USERENV('TERMINA?
----------------?
GAO?
VSIZE(X)?
返回X的大小(字節(jié))數(shù)?
SQL> select vsize(user),user from dual;
VSIZE(USER) USER?
----------- ------------------------------?
????????? 6 SYSTEM
60.AVG(DISTINCT|ALL)?
all表示對所有的值求平均值,distinct只對不同的值求平均值?
SQLWKS> create table table3(xm varchar(8),sal number(7,2));?
語句已處理。?
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)?
----------------?
???????? 3333.33
SQL> select avg(all sal) from gao.table3;
AVG(ALLSAL)?
-----------?
??? 2592.59
61.MAX(DISTINCT|ALL)?
求最大值,ALL表示對所有的值求最大值,DISTINCT表示對不同的值求最大值,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表示對所有的值求最小值,DISTINCT表示對不同的值求最小值,相同的只取一次?
SQL> select min(all sal) from gao.table3;
MIN(ALLSAL)?
-----------?
??? 1111.11
63.STDDEV(distinct|all)?
求標準差,ALL表示對所有的值求標準差,DISTINCT表示只對不同的值求標準差?
SQL> select stddev(sal) from scott.emp;
STDDEV(SAL)?
-----------?
? 1182.5032
SQL> select stddev(distinct sal) from scott.emp;
STDDEV(DISTINCTSAL)?
-------------------?
?????????? 1229.951
64.VARIANCE(DISTINCT|ALL)?
求協(xié)方差
SQL> select variance(sal) from scott.emp;
VARIANCE(SAL)?
-------------?
??? 1398313.9
65.GROUP BY?
主要用來對一組數(shù)進行統(tǒng)計?
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?
對分組統(tǒng)計再加限制條件?
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?
用于對查詢到的結(jié)果進行排序輸出?
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
轉(zhuǎn)載于:https://www.cnblogs.com/zhangwei99com/p/7379746.html
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