The user SCOTT executes the following command successfully to increase the salary values in one of his sessions: SQL> UPDATE emp SET sal=sal*1.15 WHERE deptno=20; Before SCOTT ends the transaction, user HR who has the privileges on EMP table executes a query to fetch the salary details but finds the old salary values instead of the increased values. Why does HR still see the old data?()
A、because of redo data from redo log file
B、because of data from database buffer cache
C、because of data from a temporary tablespace
D、because of undo data from the undo tablespace
You would like to display the system date in the format "Monday, 01 June, 2001".Which SELECT statement should you use?()
A、SELECT TO_DATE(SYSDATE, 'FMDAY, DD Month, YYYY') FROM dual;
B、SELECT TO_CHAR(SYSDATE, 'FMDD, DY Month, 'YYY') FROM dual;
C、SELECT TO_CHAR(SYSDATE, 'FMDay, DD Month, YYYY') FROM dual;
D、SELECT TO_CHAR(SYSDATE, 'FMDY, DDD Month, YYYY') FROM dual;
E、SELECT TO_DATE(SYSDATE, 'FMDY, DDD Month, YYYY') FROM dual;
下图所示为一个图形的绘制过程,步骤为首先完成了左侧的圆弧,第二步是绘制与圆弧相切的长度为300的直线,正在绘制右侧的圆弧。从图中显示的内容判断,正确的描述为()。
A、左侧圆弧的半径为200
B、绘制图中直线时可以不使用鼠标,键盘输入直线命令,按两次Enter键,键盘输入300,按两次Enter键
C、绘制右侧圆弧时,在圆弧命令的第一条提示后,直接按Enter键
D、功能键“正交”、“捕捉”肯定是打开的
下列关于类和对象的叙述中,错误的是( )。
A、一个类只能有一个对象
B、对象是类的具体实例
C、类是对某一类对象的抽象
D、类和对象的关系是一种数据类型与变量的关系
不属于光纤传输网的复用技术的是().
A、空分复用
B、时分复用
C、波分复用
D、频分复用
操作系统是随着硬件和软件不断发展而逐渐形成的一套()
A、数据库系统
B、软件系统
C、程序系统
D、语言系统