SQL中的單記錄函數 1.ASCII 返回與指定的字符對應的十進制數; 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,返回對應的字符; 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23' 高乾競電話 from dual; 高乾競電話 ---------------- 010-88888888轉23 4.INITCAP 返回字符串并將字符串的第一個字母變為大寫; 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,返回發現指定的字符的位置; 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 出現的位置,默認為1 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 .nchar_tst; NAME LENGTH(NAME) ADDR LENGTH(ADDR) SAL LENGTH(TO_CHAR(SAL)) ------ ------------ ---------------- ------------ --------- -------------------- 高乾競 3 北京市海錠區 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 刪除左邊出現的字符串 RTRIM 刪除右邊出現的字符串 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('HELOVEYOU','HE','I') ------------------------------ 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 假如不指定,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字的最小整數 SQL> select ceil(3.1415927) from dual; CEIL(3.1415927) --------------- 4 20.COS 返回一個給定數字的余弦 SQL> select cos(-3.1415927) from dual; COS(-3.1415927) --------------- -1 21.COSH 返回一個數字反余弦值 SQL> select cosh(20) from dual; COSH(20) --------- 242582598 22.EXP 返回一個數字e的n次方根 SQL> select exp(2),exp(1) from dual; EXP(2) EXP(1) --------- --------- 7.3890561 2.7182818 23.FLOOR 對給定的數字取整數 SQL> select floor(2345.67) from dual; FLOOR(2345.67) -------------- 2345 24.LN 返回一個數字的對數值 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 SQL> select log(2,1),log(2,4) from dual; LOG(2,1) LOG(2,4) --------- --------- 0 226.MOD(n1,n2) 返回一個n1除以n2的余數 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 返回數字n的根 SQL> select sqrt(64),sqrt(10) from dual; SQRT(64) SQRT(10) --------- --------- 8 3.1622777 33.TAN 返回數字的正切值 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 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.dd')) mon_betw from dual; MON_BETW --------- -60 39.NEW_TIME(date,'this','that') 給出在this時區=other時區的日期和時間 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,假如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 將字符數據類型轉換為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 JONES43.CONVERT(c,dset,sset) 將源字符串 sset從一個語言字符集轉換到另一個目的dset字符集 SQL> select convert('strutz','we8hp','f7dec') 'conversion' from dual; conver ------ strutz 44.HEXTORAW 將一個十六進制構成的字符串轉換為二進制 45.RAWTOHEXT 將一個二進制構成的字符串轉換為十六進制 46.ROWIDTOCHAR 將ROWID數據類型轉換為字符類型 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') 將字符串轉化為ORACLE中的一個日期 49.TO_MULTI_BYTE 將字符串中的單字節字符轉化為多字節字符 SQL> select to_multi_byte('高') from dual; TO -- 高 50.TO_NUMBER 將給出的字符轉換為數字 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函數以fmt指定的內部數字格式返回一個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() 這兩個函數都是用來對大數據類型字段進行初始化操作的函數 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 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假如是則返回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 返回當前環境變量 SQL> select userenv('language') from dual; USERENV('LANGUAGE') ---------------------------------------------------- SIMPLIFIED CHINESE_CHINA.ZHS16GBK LANG 返回當前環境的語言的縮寫 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)數 SQL> select vsize(user),user from dual; VSIZE(USER) USER ----------- ------------------------------ 6 SYSTEM60.AVG(DISTINCTALL) 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(DISTINCTALL) 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(DISTINCTALL) 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(distinctall) 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(DISTINCTALL) 求協方差 SQL> select variance(sal) from scott.emp; VARIANCE(SAL) ------------- 1398313.9 65.GROUP BY 主要用來對一組數進行統計 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 對分組統計再加限制條件 SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno having nt(*)>=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 tno ; DEPTNO COUNT(*) SUM(SAL) --------- --------- --------- 20 5 10875 30 6 9400 67.ORDER BY 用于對查詢到的結果進行排序輸出 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