出自:Oracle认证
对于雇员表（EMP）中的员工薪水（SAL）进行分级，3000元以上的为A级，2000元以上到3000元为B级，2000元及以下为C级，以下哪此操作能实现以上要求（）
A:select sal,decode(sal>3000,'A',sal>2000,'B','C') grade from emp;
B:select sal,decode(sal,3000,'A',2000,'B','C') grade from emp;
C:select sal,(case when sal>3000 then 'A' when sal>2000 then 'B' else 'C' end) grade from emp;
D:select sal,(if sal>3000 then 'A' elsif sal>2000 then 'B' else 'C' end if) grade from emp;
A SELECT statement can be used to perform these three functions: 1. Choose rows from a table. 2. Choose columns from a table 3. Bring together data that is stored in different tables by creating a link between them. Which set of keywords describes these capabilities? （）
A:difference, projection, join
B:selection, projection, join
C:selection, intersection, join
D:intersection, projection, join
E:difference, projection, product
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;
Identify the statement that correctly describes this setting.（）
What could have caused the recycle bin to clean up?（）
