字符函数

1. Upper

SELECT Upper ('abcde') FROM dual ;

SELECT * FROM emp WHERE ename=UPPER('smith') ;

2. Lower

SELECT lower('ABCDE') FROM dual ;

3. Initcap

函数INITCAP()是将每个单词的第一个字母大写,其它字母变为小写返回.

Select initcap(ename) from emp;

4. Concat

Select concat(‘a’,’b’) from dual;

Select ‘a’|| ‘b’from dual;

5. Substr

Select substr(„abcde‟,length(„abcde‟)-2)from dual;

Select substr(„abcde‟,-3,3) from dual;

6. Length

select length('abcde') from dual;

7. Replace

select replace ('abcdeffddses','s','j') from dual;

8. Instr

Instr(a,b) 找出字符串b在字符串a中出现的下标位置 Select instr('Hello World','or') from dual; 8 indexof

9. Lpad

lpad('Smith',10,'*')

左侧填充lpad() *****Smith

select lpad('Smith',10,'*') from dual;

10.Rpad

rpad('Smith',10,'*')

右侧填充rpad() Smith*****

select rpad('Smith',10,'*') from dual;

11.Trim

trim(' Mr Smith ')过滤首尾空格trim() Mr Smith

select trim(' Mr Smith ') from dual;