oracle常用函数
to_date()函数使用
select * from pstrwo where ech_date = to_date('20171211','yyyymmdd');
lower把字符串转化为小写
select lower(name) from emp;
upper把字符串转化为大写
select upper(name) from emp
replace 替换字符
select replace(name,'A','A') from emp 把名字中的A转化为a
length返回字符串长度
select * from emp where length(name) = 5 显示正好为5个字符的名字
substr()截取字符串
select substr(name,1,1) from emp; 截取名字的首字母,从第一位开始截取一位字符
显示姓名首字母大写,其余小写
select upper(substr(name,1,1)) from emp;
select lower(substr(name,2,length(name)-1)) from emp;
select upper(substr(name,1,1)) || lower(substr(name,2,length(name)-1)) from emp;
sysdate 返回系统时间
select sysdate from dual;
to_char(字符串,类型):把数据转换为字符串类型
select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') from dual;
select * from emp where to_char(emp.hiredate,'yyyy')=1980;
sys_guid()
select sys_guid() from dual;返回一个类似于UUID的唯一标识