Like any other area or field of expertise, Oracle as well requires you to adequately prepare if at all you want to excel in an interview regarding this area. You have to be well versed with the questions that are commonly asked in Oracle interviews. By doing that, you will be able to drive out fear and boost your level of confidence during the interview.
It is very easy to excel in an interview so don’t think of being afraid because you are just a step away from grasping all you need for your interview. Below are the top 20 Oracle interview questions with answers that will be very useful to you.
20 Oracle Interview Questions with Answers
1. What is the difference between Varchar and Varchar2? (answer)
Answer:
Varchar can store characters up to 2000 bytes while Varchar2 can store
characters up to 4000 bytes. Varchar holds unused space while Varchar2
releases unused space.
2. Name the various Oracle database objects
Answer: tables, tablespaces, views, indexes, and synonyms.
3. What is the work of RAW datatype in Oracle?
Answer: RAW datatype is used to store variable-length binary data or byte string values.
4. What is the use of Aggregate functions in Oracle? (answer)
Answer:
In Oracle, an aggregate function is defined as a function where values
of multiple rows or records are joined together to get a single value
output. There are some common Aggregate functions which are: Average,
Count, and Sum.
5. What is an Oracle table?
Answer:
A table as defined in Oracle, is a basic unit of data storage in the
Oracle database. A table contains information in rows and columns.
6. What is a view? (answer)
Answer: A view is defined as a logical table that is based on one or more tables or views.
7. Which language has been used to develop Oracle?
Answer: Oracle has been developed using C Language.
8. What is a nested table?
Answer: A nested table is a data type found in Oracle and is used to support columns containing multi-valued attributes.
9. What is BLOB datatype?
Answer: A BLOB data type is a varying length binary string that is used to store two gigabytes of memory.
10. What the difference is between TRANSLATE and REPLACE?
Answer: Translate is used for character by character substitution while Replace is used to substitute a single character with a word.
11. What is Merge Statement used for?
Answer:
A merge statement is used to select rows from one or more data sources
for updating and insertion into a table or a view. In simple words, you
can say it is used to combine multiple operations.
12. What are the temporal data types in Oracle?
Answer: Oracle has three temporal data types which are as follows;
- Date Data Type – Different formats of Dates
- TimeStamp Data Type – Different formats of Time Stamp
- Interval Data Type – Interval between dates and time
13. In the Oracle version 9.3.0.5.0, what does each number show?
Answer:
- 9- Major database release number
- 3- Database maintenance release number
- 0-Application server release number
- 5- Component Specific release number
- 0-Platform Specific release number
14. What is bulk copy or BCP in Oracle?
Answer:
in Oracle, bulk copy or BCP is used to import or export data from
tables and views but it doesn’t copy the structure of the same data.
15. What is the difference between a hot backup and a cold backup?
Answer:
hot backup is referred to as an online backup since it is done when the
database is still active while a cold backup is referred to as an
offline backup because it is done when the database has been shut down.
16. What is a Join used for? What are the types of Joins used in SUBQUERIES?
Answer:
a join is basically used to combine and compare specific rows of data
from two or even more tables in a database. Types of joins are as
follows:
- Outer Join – to join matching data and some dissimilar data from more than one table.
- Self Join – to join a table with itself.
- Equi-join
17. What are the attributes of cursor?
Answer: cursor has the following attributes:
- %FOUND – this has three functions which are: returning NULL if cursor is open and fetch has not been executed, returning False if no rows are returned and finally returning TRUE if the fetch of cursor is executed successfully.
- %NOT FOUND – this one too performs three functions: it returns True if no row was returned, it returns False if fetch has been executed and finally it returns NULL if cursor is open and fetch has not been executed.
- %ISOPEN – this one returns true if the cursor is open and also returns false if the cursor is closed.
- %ROWCOUNT – this one returns the number of rows fetched.
18. What are the different constraints used in Oracle?
Answer:
- NOT NULL – indicates that a particular column cannot contain NULL values.
- NULL – indicates that a particular column can contain NULL values.
- DEFAULT – indicates the value is assigned to default value.
- CHECK – this one validates that values in a given column meet the specific criteria.
19. What is Integrity Constraint?
Answer:
Integrity Constraint is defined as a declaration that defines a
business rule for a table. Common types of Integrity Constraints are
Domain Integrity and Referential Integrity.
20. What are the types of synonyms?
Answer: there are two types of synonyms namely:
- Private – this can only be accessed by the owner.
- Public – this one is not limited and it can be accessed by any database user.
That's all about the frequently asked Oracle database interview questions for 3 to 5 years experienced professionals. You can use these questions to quickly revise the key Oracle concepts before going for interview. In conclusion, I can confidently say that the above mentioned questions are up to date and are the questions that you will meet during your Oracle interview.
If you go through them keenly and understand all of
them I promise you that you will have a very easy time during the
interview and you will even be sure of getting the job.
This is
the real deal for you. Go through these questions over and over again
and you will eventually master everything and you will be good to go.
Your confidence will improve and you will now see things in a different
perspective. Always remember that preparations is very important in any
type of interview. I wish you the best of luck.
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