Professional Oracle Certification Interview Questions & Answers:

1. What will be the output for this query:
select 1 from dual minus select a from dual;

This will produce Error:
Expression must have same datatype as corresponding expression

2. Explain Which two statements are true regarding working with dates? (Choose two.)
A. The default internal storage of dates is in the numeric format
B. The default internal storage of dates is in the character format
C. The RR date format automatically calculates the century from the SYSDATE function and does
not allow the user to enter the century
D. The RR date format automatically calculates the century from the SYSDATE function but allows
the user to enter the century if required?

A. The default internal storage of dates is in the numeric format
D. The RR date format automatically calculates the century from the SYSDATE function but allows
the user to enter the century if required

3. Explain What are transportable table spaces and the need to use them?

Transportable tablespaces are the fastest way for moving large volume of data between two oracle databases. We can use the transportable tablespaces feature to copy a set of tablespaces from one oracle database to another. Moving data using transportable tablespaces is much faster than performing either an export/import or unload/load the same data.

4. What are transportable table spaces and the need to use them?

Transportable tablespaces are the fastest way for moving large volume of data between two oracle databases. We can use the transportable tablespaces feature to copy a set of tablespaces from oneoracle database to another. Moving data using transportable tablespaces is much faster than performing either an export/import or unload/load the same data.

5. Which three statements are true regarding subqueries? (Choose three.)
A. Subqueries can contain GROUP BY and ORDER BY clauses
B. Main query and subquery can get data from different tables
C. Main query and subquery must get data from the same tables
D. Subqueries can contain ORDER BY but not the GROUP BY clause
E. Only one column or expression can be compared between the main query and subqeury
F. Multiple columns or expressions can be compared between the main query and subquery

A. Subqueries can contain GROUP BY and ORDER BY clauses
B. Main query and subquery can get data from different tables
F. Multiple columns or expressions can be compared between the main query and subquery

6. You need to calculate the number of days from 1st Jan 2007 till date:
Dates are stored in the default format of dd-mm-rr.
Which two SQL statements would give the required output? (Choose two.)
A. SELECT SYSDATE - 01-JAN-2007 FROM DUAL
B. SELECT SYSDATE - TO_DATE(01/JANUARY/2007) FROM DUAL;
C. SELECT SYSDATE - TO_DATE(01-JANUARY-2007) FROM DUAL;
D. SELECT TO_CHAR(SYSDATE,DD-MON-YYYY)-01-JAN-2007 FROM DUAL;
E. SELECT TO_DATE(SYSDATE,DD/MONTH/YYYY)-01/JANUARY/2007 FROM DUAL;

B. SELECT SYSDATE - TO_DATE('01/JANUARY/2007') FROM DUAL;
C. SELECT SYSDATE - TO_DATE('01-JANUARY-2007) FROM DUAL;

7. Suppose you need to generate a list of all customer last names with their credit limits from the
CUSTOMERS table. Those customers who do not have a credit limit should appear last in the list.
Which two queries would achieve the required result? (Choose two.)
A. SELECT cust_last_name,cust_credit_limit
FROM customers
ORDER BY cust_credit_limit DESC;
B. SELECT cust_last_name,cust_credit_limit
FROM customers
ORDER BY cust_credit_limit;
C. SELECT cust_last_name,cust_credit_limit
FROM customers
ORDER BY cust_credit_limit NULLS LAST;
D. SELECT cust_last_name,cust_credit_limit
FROM customers
ORDER BY cust_last_name,cust_credit_limit NULLS LAST;

B. SELECT cust_last_name,cust_credit_limit
FROM customers
ORDER BY cust_credit_limit;
C. SELECT cust_last_name,cust_credit_limit
FROM customers
ORDER BY cust_credit_limit NULLS LAST;

8. Which two statements are true regarding views? (Choose two.)
A. A subquery that defines a view cannot include the GROUP BY clause
B. A view is created with the subquery having the DISTINCT keyword can be updated
C. A view that is created with the subquery having the pseudo column ROWNUM keyword cannot
be updated
D. A Data Manipulation Language (DML) operation can be performed on a view that is created
with the subquery having all the NOT NULL columns of a table

C. A view that is created with the subquery having the pseudo column ROWNUM keyword cannot
be updated
D. A Data Manipulation Language (DML) operation can be performed on a view that is created
with the subquery having all the NOT NULL columns of a table

9. Explain Which two statements are true regarding views? (Choose two.)
A. A subquery that defines a view cannot include the GROUP BY clause
B. A view is created with the subquery having the DISTINCT keyword can be updated
C. A view that is created with the subquery having the pseudo column ROWNUM keyword cannot
be updated
D. A Data Manipulation Language (DML) operation can be performed on a view that is created
with the subquery having all the NOT NULL columns of a table

C. A view that is created with the subquery having the pseudo column ROWNUM keyword cannot
be updated
D. A Data Manipulation Language (DML) operation can be performed on a view that is created
with the subquery having all the NOT NULL columns of a table

10. Explain Which two statements are true regarding constraints? (Choose two.)
A. A foreign key cannot contain NULL values
B. A columns with the UNIQUE constraint can contain NULL values
C. A constraint is enforced only for the INSERT operation on a table
D. A constraint can be disabled even if the constraint column contains data
E. All constraints can be defined at the column level as well as the table level

B. A columns with the UNIQUE constraint can contain NULL values
D. A constraint can be disabled even if the constraint column contains data