字符串的拼接
select concat('4', to_char(02, '09')) from dual;
select concat('4', to_char(02)) from dual;
select 4 || '02' from dual;
为什么结果不一样呢，我想用to_char达到select 4 || '02' from dual;的效果怎么弄呀
[解决办法]
SELECT concat('4',to_char(02, 'FM09')) from dual;