摘要：参数定义 ROUND_CEILING Rounding mode to round towards positive infinity. 向正无穷方向舍入 ROUND_DOWN Rounding mode to round towards zero. 向零方向舍入 ROUND_FLOOR Round 阅读全文

摘要：1、改密码 (1).打开doc命令框键入：sqlplus /nolog (2).输入：connect / as sysdba (3).修改密码：alter user userName identified by passWord; (4).解锁：alter user userName account 阅读全文

摘要：exists : 强调的是是否返回结果集，不要求知道返回什么, 比如： select name from student where sex = 'm' and mark exists(select 1 from grade where ...) ,只要exists引导的子句有结果集返回，那么exi 阅读全文