Oracle SQL 內置函數大全(3)

Oracle幫您準確洞察各個物流環節

43.CONVERT(c,dset,sset)將源字元串 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 將一個十六進位構成的字元串轉換為二進位

45.RAWTOHEXT 將一個二進位構成的字元串轉換為十六進位

46.ROWIDTOCHAR 將ROWID數據類型轉換為字元類型

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") 將字元串轉化為ORACLE中的一個日期

49.TO_MULTI_BYTE 將字元串中的單位元組字元轉化為多位元組字元SQL> select to_multi_byte("高") from dual;

TO--高

50.TO_NUMBER將給出的字元轉換為數字SQL> select to_number("1999") year from dual;

YEAR---------1999

51.BFILENAME(dir,file)指定一個外部二進位文件SQL>insert into file_tb1 values(bfilename("lob_dir1","image1.gif"));

52.CONVERT("x","desc","source") 將x欄位或變數的源source轉換為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 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 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,D

54.EMPTY_BLOB()和EMPTY_CLOB()這兩個函數都是用來對大數據類型欄位進行初始化操作的函數

55.GREATEST返回一組表達式中的最大值,即比較字元的編碼大小.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 userUSER 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,VSIZEISDBA 查看當前用戶是否是DBA如果是則返回trueSQL> select userenv("isdba") from dual;

USEREN------FALSESQL> select userenv("isdba") from dual;

USEREN------TRUESESSION返回會話標誌SQL> select userenv("sessionid") from dual;

USERENV("SESSIONID")--------------------152ENTRYID返回會話人口標誌SQL> select userenv("entryid") from dual;

USERENV("ENTRYID")------------------0INSTANCE返回當前INSTANCE的標誌SQL> select userenv("instance") from dual;

USERENV("INSTANCE")-------------------1LANGUAGE返回當前環境變數SQL> select userenv("language") from dual;

USERENV("LANGUAGE")----------------------------------------------------SIMPLIFIED CHINESE_CHINA.ZHS16GBKLANG返回當前環境的語言的縮寫SQL> select userenv("lang") from dual;

USERENV("LANG")----------------------------------------------------ZHSTERMINAL返回用戶的終端或機器的標誌SQL> select userenv("terminal") from dual;

USERENV("TERMINA----------------GAOVSIZE(X)返回X的大小(位元組)數SQL> select vsize(user),user from dual;

VSIZE(USER) USER----------- ------------------------------6 SYSTEM