字元型 ASCII CHR chr(39) chr(10) chr(9) LOWER UPPER INITCAP CONCAT || SUBSTR LENGTH INSTR TRIM dump lpad rpad REPLACE translate ('ABCDEFABCXYZ','ACB','abc') ASCII('字元') 返回字元的ASCII碼值 idle> select ASCII('a') from dual; ASCII('A') ---------- 97 idle> select ASCII('A') from dual; ASCII('A') ---------- 65 idle> CHR('n') 返回n的字元值 n是ASCII碼數 idle> select chr(65) from dual; C - A idle> select chr(39) from dual; C - ' idle> 但是求單引號的ASCII碼寫法很特殊 兩個單引帶表一個單引 idle> select ASCII(''') from dual; ERROR: ORA-01756: quoted string not properly terminated idle> select ASCII('''') from dual; ASCII('''') ----------- 39 idle> LOWER(列名|表示式) 小寫轉換 idle> select lower('ABC') from dual; LOW --- abc idle> dual 為虛表,當一個語句不需要從表中獲取資料時,但又要維持SQL語法,oracle才提供了虛表來解決這個問題 UPPER(列名|表示式) 大寫轉換 idle> select upper('abc') from dual; UPP --- ABC idle> INITCAP(列名|表示式) 每個詞的詞頭大寫 其他小寫 idle> select initcap('abC dEf XYZ') from dual; INITCAP('AB ----------- Abc Def Xyz idle> CONCAT(列名|表示式,列名|表示式) 將第一個字串和第二個字串連線 idle> select concat('abc','xyz') from dual; CONCAT ------ abcxyz 不太常用,因為我們可以用 || 連線 idle> select 'abc'||'xyz' from dual; 'ABC'| ------ abcxyz idle> SUBSTR(列名|表示式,m,[n]) 返回指定子串,該子串是從第m個字元開始,其長度為n,不指定n值則從m到最後 idle> select substr('abcdefxyz',4,3) from dual; SUB --- def idle> select substr('abcdefxyz',4) from dual; SUBSTR ------ defxyz idle> LENGTH(列名|表示式) 返回字串的長度 idle> select length('abcdefxyz') from dual; LENGTH('ABCDEFXYZ') ------------------- 9 idle> INSTR (列名|表示式,'字串',[m],[n]) 從表示式或列中搜索給定的字串的所處位置,m代表從第幾個開始搜,n代表第幾次出現. m和n預設都是1 idle> select INSTR('abcdddxyz','d') from dual; INSTR('ABCDDDXYZ','D') ---------------------- 4 idle> idle> select INSTR('abcdddxyz','d',5) from dual; INSTR('ABCDDDXYZ','D',5) ------------------------ 5 idle> select INSTR('abcdddxyz','d',5,2) from dual; INSTR('ABCDDDXYZ','D',5,2) -------------------------- 6 idle> TRIM([leading|]trailing|both 要去掉的字元 FROM 源字串) 從源字串中去掉指定的字元 可以用leading tailing來修飾去掉的字串是在開頭或結尾,預設是兩者都 預設擷取的是空格 idle> select trim('a' from 'aaabcdeaaafxyzaaa') from dual; TRIM('A'FRO ----------- bcdeaaafxyz idle> select trim(leading 'a' from 'aaabcdeaaafxyzaaa') from dual; TRIM(LEADING'A -------------- bcdeaaafxyzaaa idle> select trim(trailing 'a' from 'aaabcdeaaafxyzaaa') from dual; TRIM(TRAILING' -------------- aaabcdeaaafxyz idle> 左補齊lpad 右補齊rpad 將不足20個字元的位置用指定符號填充. idle> select lpad(ename,20,'-') ,rpad(ename,20,'-') from emp where ename like 'S%'; LPAD(ENAME,20,'-') RPAD(ENAME,20,'-') -------------------- -------------------- ---------------SMITH SMITH--------------- ---------------SCOTT SCOTT--------------- idle> REPLACE(源字串,OLD字串,NEW字串) 從源字串中找到搜尋的old字串,替換成new字串 idle> select replace('abcdefxyz','def','DEF') from dual; REPLACE(' --------- abcDEFxyz idle> dump('str'[,FMT[,S,E]]) 用於轉換進位制格式 str 被轉換的字串 FMT 格式 S str的開始字元位置 E S開始的後續結束字元位置 SQL> select dump('abcd') from dual; DUMP('ABCD') -------------------------- Typ=96 Len=4: 97,98,99,100 SQL> SQL> select dump('abcd',1002) from dual; DUMP('ABCD',1002) ------------------------------------------------ Typ=96 Len=4 CharacterSet=AL32UTF8: 97,98,99,100 SQL> SQL> select dump('abcd',1008) from dual; DUMP('ABCD',1008) --------------------------------------------------- Typ=96 Len=4 CharacterSet=AL32UTF8: 141,142,143,144 SQL> DUMP('ABCD',1016) ----------------------------------------------- Typ=96 Len=4 CharacterSet=AL32UTF8: 61,62,63,64 SQL> select dump('abcd',1017) from dual; DUMP('ABCD',1017) ------------------------------------------- Typ=96 Len=4 CharacterSet=AL32UTF8: a,b,c,d SQL> SQL> select dump('abcd',1017,2,2) from dual; DUMP('ABCD',1017,2,2) --------------------------------------- Typ=96 Len=4 CharacterSet=AL32UTF8: b,c SQL> SQL> select dump('飛') from dual; DUMP('飛') ------------------------- Typ=96 Len=3: 233,163,158 SQL> select 233*power(256,2)+163*256+158 from dual; 233*POWER(256,2)+163*256+158 ---------------------------- 15311774 SQL> select chr(15311774) from dual; CHR --- 飛 SQL> 單行函式的例子 idle> select concat(ename,job) "EMP",substr(job,1,5) title,length(ename),instr(ename,'T',1,2) from emp where lower(ename) = 'scott'; EMP TITLE LENGTH(ENAME) INSTR(ENAME,'T',1,2) ------------------- ----- ------------- -------------------- SCOTTANALYST ANALY 5 5