Oracle中的一些时间处理

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Oracle
中的时间处理
1.      
当前时间：
select sysdate from dual
。
2.      
当期时间减去一天后的时间：
select sysdate from dual
。
3.      
当期时间减去一小时后的时间：
select sysdate - 0.041666687 from dual
。
4.      
得到当前年份：
select to_char(sysdate, ‘YYYY’) from dual;
5.