【正文】 onesmartin MARTIN Martinblake BLAKE Blakeclark CLARK Clarkking KING Kingturner TURNER Turnerjames JAMES Jamesford FORD Fordmiller MILLER Miller小寫 大寫 首字母大寫Select lower(39。mf TR39。), upper(39。mf TR39。), initcap(39。mf TR39。) from dual。LOWER(39。MFTR39。) UPPER(39。MFTR39。) INITCAP(39。MFTR39。) mf tr MF TR Mf TrDual是虛表，讓我們用表的形式來訪問函數(shù)的值。其它字符串操作函數(shù)select ename,job,concat(ename,job) from emp。ENAME JOB CONCAT(ENAME,JOB) SMITH CLERK SMITHCLERKALLEN SALESMAN ALLENSALESMANWARD SALESMAN WARDSALESMANJONES MANAGER JONESMANAGERMARTIN SALESMAN MARTINSALESMANBLAKE MANAGER BLAKEMANAGERCLARK MANAGER CLARKMANAGERKING PRESIDENT KINGPRESIDENTTURNER SALESMAN TURNERSALESMANJAMES CLERK JAMESCLERKFORD ANALYST FORDANALYSTMILLER CLERK MILLERCLERK將兩個(gè)字符連接到一起下面三句話是求字符串的長度，字符串要單引。select length(39。張三39。) from dual。按照字select lengthb(39。張三39。) from dual。按字節(jié)select lengthc(39。張三39。) from dual。unicode的長度SQL select length(39。張三39。) from dual。LENGTH(39。張三39。) 2SQL select lengthb(39。張三39。) from dual。LENGTHB(39。張三39。) 4SQL select lengthc(39。張三39。) from dual。LENGTHC(39。213。197。200。253。39。) 2select ename,substr(ename,1,1) first,substr(ename,1) lastfrom emp。ENAME first last SMITH S HALLEN A NWARD W DJONES J SMARTIN M NBLAKE B ECLARK C KKING K GTURNER T RJAMES J SFORD F DMILLER M Rsubstr(字符串,m,n),m是從第幾個(gè)字符開始，如果為負(fù)的意思是從后邊的第幾個(gè)開始。N是數(shù)多少個(gè)，如果不說就是一直到字符串的結(jié)尾。select ename,instr(ename,39。A39。) A在第幾位 from emp。ENAME A在第幾位 SMITH 0ALLEN 1WARD 2JONES 0MARTIN 2BLAKE 3CLARK 3KING 0TURNER 0JAMES 2FORD 0MILLER 0求子串在父串中的位置，0表示沒有在父串中找到該子串。截?cái)嘧址吞砑幼址暮瘮?shù)SQL select trim(leading 39。a39。 from 39。aaaaabababaaaaa39。) from dual。TRIM(LEADING39。A39。FROM39。AAAAABABABbababaaaaa截掉連續(xù)的前置的aSQL select trim(trailing 39。a39。 from 39。aaaaabababaaaaa39。) from dual。TRIM(TRAILING39。A39。FROM39。AAAAABABAaaaaababab截掉連續(xù)的后置的aSQL select trim(both 39。a39。 from 39。aaaaabababaaaaa39。) from dual。TRIM(BOTH39。A39。FROM39。AAAAABABABAAAbabab截掉連續(xù)的前置和后置的aSQL select trim(39。a39。 from 39。aaaaabababaaaaa39。) from dual。TRIM(39。A39。FROM39。AAAAABABABAAAAA39。)Babab如果不說明是前置還是后置就是both全截?cái)?。Trim函數(shù)是截掉頭或者尾連續(xù)的字符，一般我們的用途是去掉空格。SQL select lpad(ename,20,39。39。) ename,rpad(ename,20,39。39。) ename from emp。ENAME ENAME SMITH SMITHALLEN ALLENWARD WARDJONES JONESMARTIN MARTINBLAKE BLAKECLARK CLARKKING KINGTURNER TURNERJAMES JAMESFORD FORDMILLER MILLER左鋪墊和右鋪墊，20是總共鋪墊到多少位，是要鋪墊的字符串。SQL select lpad(sal,2,39。 39。) ename,rpad(sal,10,39。 39。) ename,sal from emp。別名 別名ENAME 位數(shù)不足 ENAME 左對齊 SAL 80 800 80016 1600 160012 1250 125029 2975 297512 1250 125028 2850 285024 2450 245050 5000 500015 1500 150095 950 95030 3000 300013 1300 1300Lpad左鋪墊，rpad右鋪墊，一般的用途是美化輸出的結(jié)果。如果位數(shù)不足，按照截取后的結(jié)果顯示，不報(bào)錯(cuò)。SELECT REPLACE(39。JACK and JUE39。,39。J39。,39。BL39。) FROM DUAL。BLACK and BLUE將字符串中的J全部替換位BL實(shí)驗(yàn)13：操作數(shù)字的函數(shù)該實(shí)驗(yàn)的目的是掌握常用的關(guān)于數(shù)字操