select * from li.books where book_publish_date between '1-2月-2005' and '1-2月-2010';select * from books where book_price between 50 and 60;select * from books where catalog_id in (select catalog_id from catalogs where catalog_name='数据库');select * from catalogs;---dual 表select * from dual;-获取oracle 的系统日期select sysdate from dual;--为前日期增加10天select sysdate+10 from dual;select (select from dual)+10 from dual;--日期函数select add_months(sysdate,4) from dual;select add_months('2-2月-1990',4) from dual;-获取指定月份的最后一天select last_day(sysdate) from dual;select last_day('2-2月-2014') from dual;---计算两个月之间相差几个月select months_between(sysdate,'27-4月-2014') from dual;----日期的四舍五入---按年select round(sysdate,'year') from dual;--按月select round(sysdate,'month') from dual;select round((select to_date('1987-4-15','yyyy-mm-dd') from dual),'month') from dual;select to_date('1987-3-1','yyyy-mm-dd') from dual--按周select round(sysdate,'day') from dual;--next_day 的使用， 获取指定日期的下一天所在的日期select next_day(sysdate,2) from dual; 下一周的第几天;select next_day('27-8月-2014',2) from dual; --阶段当前日期 --按年 select trunc(sysdate,'year') from dual; --按月 select trunc(sysdate,'month') from dual; --按周 select trunc(sysdate,'day') from dual; --比较一组数字中的最大值 select greatest(12,22,33,13,45,5) from dual; select greatest ( '12-5月-2014', '12-12月-2011', '12-3月-2000' ) from dual; ---字符串函数的使用--截断字符串（从第n个字符开始截取，截取的长度为m个字符）select substr('helloworld',3,5) from dual;--获取指定字符串中的字符位置select instr('hello','o') from dual;--获取字符串的长度select length('liuhuahua') from dual;--转换函数--将其他类型的数据转为字符串（最常用的是日期转字符串）--日期转字符串select to_char(sysdate,'yyyy-mm-dd') from dual;select sysdate from dual;--将数字转为字符串select to_char(9898.33,'$99999.999') from dual;--将其他数据转为日期格式（通常是将字符串转为日期）select to_date('1987-3-1','yyyy-mm-dd') from dual;--日期比大小，获取一组日期的最大值select greatest(to_date('2024-4-22','yyyy-mm-dd'),to_date('2024-5-1','yyyy-mm-dd'),to_date('2014-12-22','yyyy-mm-dd')) from dual;select '4'+'5' from dual;select 4+5 from dual;--获取用户的登陆idselect uid from books;select user from dual;--聚合函数select sum(book_price) from books; select count(book_id) from books;---oracle的分页显示 select * from (select books.* ,rownum r from books where rownum2; select books.*, rownum from books where rownum=100 order by catalog_id;