题目内容

以下哪条语句是错误的?()

A. SELECTename,salsalaryFROMempORDERBYsal;
B. SELECTename,salsalaryFROMempORDERBYsalary;
C. SELECTename,salsalaryFROMempORDERBY3;
D. SELECTenameFROMempORDERBYsalDESC;

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DEFINE命令可用于定义哪种变量?()

A. NUMBER
B. CHAR
C. VARCHAR2
DATE

以下哪条语句是正确的?()

A. SELECTdeptno,sum(sal)FROMemp;
B. SELECTdeptno,sum(sal)FROMempWHEREavg(sal)>2000GROUPBYdeptno;
C. SELECTdeptno,sum(sal)FROMempGROUPBYdeptnoHAVINGavg(sal)>2000;
D. SELECTdeptno,sum(sal)FROMempWHEREavg(sal)>2000ORDERBYdeptno;

下面哪条命令可以显示表的结构()

A. DESC
B. PPEND
C. DISC
DEFINE

例程恢复是由哪个后台进程来完成的?()

A. DBWR
B. LGWR
C. SMON
D. PMON

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