Here are some of the top Oracle Exam Interview Questions and Answers, if you wish t have more details regarding the Oracle Certification Exam, you should check out the training courses which are offered at the SPOTO Club.

1. Difference between varchar and varchar2 data types?
Varchar could store up to 2000 bytes and varchar2 could store up to 4000 bytes. Varchar would be occupied space for NULL values and Varchar2 wouldn’t be occupied any space. Both would have differed concerning space.

2. Oracle has been developed in which language?
Oracle has been developed utilizing the C Language.

3. What would be RAW datatype?
RAW datatype would be utilized for storing values in binary data format. The greatest size for a raw in a table in 32767 bytes.

4. What would be the use of the NVL function?
The NVL function would be utilized for replacing NULL values with another or given value. For instance is – NVL (Value, replace value)

5. Whether any commands would be utilized for Month’s calculation? If so, What would be they?
In Oracle, months_between function is utilized for finding the number of months between the given dates. The illustration is – Months_between(Date 1, Date 2)

6. What are nested tables?
A nested table is considered to be a data type in Oracle that would be utilized to support columns containing multi-valued attributes. It would also be holding the entire sub table.

7. What is the COALESCE function?
COALESCE function is utilized for returning the value which would be set to be not null in the list. If all values in the list would be null, then the coalesce function would be returning NULL. Coalesce(value1, value2,value3,…)

8. What is BLOB datatype?
A BLOB data type is considered to be a varying length binary string which would be utilized to store two gigabytes memory. The length would be mentioned in Bytes for the BLOB.

9. How could we represent comments in Oracle?
Comments in Oracle could be represented in two ways –
1. Two dashes(–) before starting of the line – Single statement.
2. /*—— */ would be utilized to represent it as comments for the block of the statement.

10. What is DML?
DML (Data Manipulation Language) would be utilized for accessing and manipulating data in the existing objects. DML statements would be insert, select, update as well as delete and it won’t implicitly be committed to the current transaction.

11. Differentiate between TRANSLATE and REPLACE?
Translate is utilized for character by character substitution and Replace is utilized for substituting a single character with a word.

12. How do we demonstrate rows from the table without duplicates?
Duplicate rows could be removed by utilizing the keyword DISTINCT in the select statement.

13. What would be the usage of the Merge Statement?
Merge statement is utilized to select rows from one or more data source for updating as well as insertion into a table or a view. It is utilized for combining multiple operations.

14. What is NULL value?
The NULL value would be representing missing or unknown data. This is utilized as a place holder or represented it in as default entry for indicating that there would be no actual data present.

15. Explain USING Clause with examples?
The USING clause is utilized for specifying with the column to test for equality when two tables would be joined.
Example: [sql]select * from employee join salary utilizing employee ID[/sql]
Employee tables unite with the Salary tables with the Employee ID.

So, these were some of the Oracle Exam’s Interview Question and Answers. For further help, you could check out the training courses which are being offered at the SPOTO Club.