大小寫
upper所有大寫 A-Z
lower所有小寫 a-z
initcap 開頭大寫，其餘小寫
SQL> select ename from emp where deptno=10;
ENAME
----------
CLARK
KING
MILLER
SQL> select lower(ename) from emp where deptno=10;
LOWER(ENAM
----------
clark
king
miller
SQL> select initcap(ename) from emp where deptno=10;
INITCAP(EN
----------
Clark
King
Miller
SQL>
SQL> select initcap('tiger_scott') from dual;
INITCAP('TI
-----------
Tiger_Scott
SQL> select initcap('tiger8scott') from dual;
INITCAP('TI
-----------
Tiger8scott
SQL>
字符函數concat
SQL> select concat(ename,' is work'),job from emp;
CONCAT(ENAME,'ISWO JOB
------------------ ---------
SMITH is work CLERK
ALLEN is work SALESMAN
WARD is work SALESMAN
JONES is work MANAGER
MARTIN is work SALESMAN
BLAKE is work MANAGER
CLARK is work MANAGER
SCOTT is work ANALYST
KING is work PRESIDENT
TURNER is work SALESMAN
ADAMS is work CLERK
CONCAT(ENAME,'ISWO JOB
------------------ ---------
JAMES is work CLERK
FORD is work ANALYST
MILLER is work CLERK
14 rows selected.
SQL>
切割
substr（expr，m，n）#m：從哪開始+|- num，n：取多少個n>0
substr('mygodssr',1,1)-->m
substr('mygodssr',-1,1)-->r
SQL> select ename from emp where substr(ename,2,1)='A';
ENAME
----------
WARD
MARTIN
JAMES
SQL>
長度
SQL> select length(ename),ename from emp;#返回字符長度
LENGTH(ENAME) ENAME
------------- ----------
5 SMITH
5 ALLEN
4 WARD
5 JONES
6 MARTIN
5 BLAKE
5 CLARK
5 SCOTT
4 KING
6 TURNER
5 ADAMS
LENGTH(ENAME) ENAME
------------- ----------
5 JAMES
4 FORD
6 MILLER
14 rows selected.
SQL>
SQL> insert into emp(empno,ename) values(1,'數');
1 row created.
SQL> select ename,length(ename),lengthc(ename),lengthb(ename) from emp where empno=1;
ENAME LENGTH(ENAME) LENGTHC(ENAME) LENGTHB(ENAME) #3個字節存一個漢字--》2個字符
---------- ------------- -------------- --------------
??? 3 3 9
SQL>
查找
SQL> select instr(ename,'A'),ename from emp;
INSTR(ENAME,'A') ENAME
---------------- ----------
0 SMITH 沒找到
1 ALLEN 第一個
2 WARD 第二個
0 JONES
2 MARTIN
3 BLAKE 第三個
1 ADAMS 多個A只找第一個
SQL> select ename from emp where instr(substr(ename,1,2),'A')=1;
ENAME
----------
ALLEN
ADAMS
SQL>
右|左對齊
SQL> select deptno,dname,loc from dept;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
SQL> select rpad(deptno,10,' ')deptno,dname,loc from dept;
DEPTNO DNAME LOC
---------------------------------------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
SQL>
SQL> select lpad(deptno,8,' ')deptno,dname,loc from dept;
DEPTNO DNAME LOC
-------------------------------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
SQL>
SQL> col dname just right; #使dname列靠右
SQL> select deptno,dname,loc from dept;
DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
SQL>
切除
SQL> select trim('a' from 'aaabbbbaaa') from dual;
TRIM
----
bbbb
SQL> select trim(trailing 'a' from 'aaabbbbaaa') from dual;
TRIM(TR
-------
aaabbbb
SQL> select trim(leading 'a' from 'aaabbbbaaa') from dual;
TRIM(LE
-------
bbbbaaa
SQL>
SQL> select ename,trim('A' from ename) from emp;
ENAME TRIM('A'FR
---------- ----------
SMITH SMITH
ALLEN LLEN
替換
replace（expr，old，new）
SQL> select replace('ssr and ssy','ss','mm') from dual;
REPLACE('SS
-----------
mmr and mmy
SQL>