oracle之sql（二）

大小写

upper所有大写 A-Z
lower所有小写 a-z
initcap 开头大写，其余小写

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>

字符函数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：从哪开始+|- num，n：取多少个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>

长度

SQL> select length(ename),ename from emp;#返回字符长度

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,'数');

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个字节存一个汉字--》2个字符
---------- ------------- -------------- --------------
??? 3 3 9

SQL>

查找

SQL> select instr(ename,'A'),ename from emp;

INSTR(ENAME,'A') ENAME
---------------- ----------
0 SMITH 没找到
1 ALLEN 第一个
2 WARD 第二个
0 JONES
2 MARTIN
3 BLAKE 第三个
1 ADAMS 多个A只找第一个

SQL> select ename from emp where instr(substr(ename,1,2),'A')=1;

ENAME
----------
ALLEN
ADAMS

SQL>

右|左对齐

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

替换

replace（expr，old，new）

SQL> select replace('ssr and ssy','ss','mm') from dual;

REPLACE('SS
-----------
mmr and mmy

SQL>