Database Management System

In SQL, which command is used to select only one copy of each set of duplicable rows

• SELECT UNIQUE

• SELECT DIFFERENT

• SELECT *

• SELECT DISTINCT

• None of the above

Which of the following queries are legal?

• SELECT deptno, avg(sal) FROM emp;

• SELECT deptno, count(deptno) FROM emp GROUP BY ename;

• SELECT deptno, count(deptno), job FROM emp GROUP BY deptno;

• SELECT deptno, avg(sal) FROM emp GROUP BY deptno;

Which of the following SQL operations demands the use of wild cards comparisons?

• LIKE

• EXISTS

• BETWEEN

• IN

A data block is

• the largest logical storage unit for a database object

• the smallest logical storage unit for a database object

• the place where all deleted records are persisted

• the largest logical storage unit ever available for any database block

• all of the above

All of the following can only be used with numeric data types except:

• AVG

• COUNT

• SUM

• STDDEV

• None of the above

_______________ are padded with space characters to match the specified length.

• VARCHAR

• VARCHAR2

• CHAR

• CHAR2

How should a many-to-many relationship be handled?

• By adding an join entity table

• By adding intersection entity table

• By adding union entity table

• By adding Cartesian entity table

A foreign key column must contain unique values.

• True

• False

Delete and truncate command in SQL

• retrieve rows in a table

• remove some part of a table

• remove all rows in a table

• recover all the rows deleted in a table.

Which of the following statements regarding primary key is false?

• Primary key can not have null values

• Primary key may contain duplicate values

• Primary key can not be applied for multiple columns

• All of the above