Oracle Interview Questions

Let’s go into detail about each round: 

1. Online Coding Round: First of all, an online test round is conducted where Multiple Choice Questions ranging from logical reasoning, and quantitative analysis to core subjects such as Data Structures and Algorithms, Networking, Object Oriented Programming, Database Management Systems are asked.
2. Technical Interview Round 1: In the Technical Interview Round, a video call or a phone call is scheduled with the candidate and his or her coding skills are assessed. The interviewer generally asks two questions to the candidate based on Data Structures and Algorithms.
3. Technical Interview Round 2: This is a personal interview round where tricky and complex questions based on data structures are asked. Questions related to the CV of the candidate may also be asked in this round. Also, some interviewers like to ask puzzles to test the thinking ability of the candidate.
4. HR Round: This is an informal round where the interviewer can ask general questions about the candidate’s work experience and questions related to ethics. This helps the company to decide whether the applicant is a cultural fit for their company.

Now that we know a bit about the work culture at Oracle, I am sure that you are tempted to interview at Oracle and take a job! Their hiring process is a crucial part of their culture as they care deeply about their teams and the people who make them up. Building a more representative and inclusive workplace is the motive of Oracle’s hiring team, and that begins with hiring highly skilled people from various backgrounds. According to Oracle’s hiring team, in order to truly build for everyone, a diversity of perspectives and experiences, and a fair hiring process is the first step in getting there. Let us learn more about what the hiring process at Oracle looks like:-

Written below is a query to find out the student with the 2nd rank from the table STUDENTS_DETAILS:-

SELECT TOP 1 rank FROM (SELECT TOP 2 rank FROM STUDENT_DETAILS ORDER BY rank DESC) AS STUDENT ORDER BY rank ASC; 

The ROWS option in the IMP command can be used to indicate whether the table rows should be imported or not.

The IGNORE option in the IMP command can be used to understand how object creation errors should be handled.

The INDEXES option in the IMP command can be used to determine whether indexes are imported or not.

The INDEXES option in the IMP command can be used to determine whether indexes are imported or not.

SELECT to_char(to_date('12-07-2021', 'DD-MM-YYYY'), 'YYYY-MM-DD') FROM dual;

As we can see from the above example, the to_char() function can be used to convert a date to char in Oracle.

SELECT to_date ('2021-07-12', 'YYYY/MM/DD') FROM dual;

As we can see from the above example, the to_date() function can be used to convert a string to a date in Oracle.

The SYSDATE() function can be used to find the current date and time of the operating system on which the Oracle database is running. The example given below shows how to do the same:-

SELECT TO_CHAR (SYSDATE, 'YYYY-MM-DD HH24:MI:SS') "Current Date:" FROM DUAL;

Actual parameters are defined as the variables or expressions referenced in the parameter list of a subprogram. An example of a procedure call that lists two actual parameters named empNumber and amount is as follows:-

updateSalary(empNumber,amount);

Formal parameters can be defined as variables declared in a subprogram specification and referenced in the subprogram body. An example of a procedure that declares two formal parameters named empID and amount: is as follows:-

PROCEDURE updateSalary(empID INTEGER, amount REAL) IS currentSalary REAL;

A query to find the average salary of employees from the Emp Oracle Table is given below:-

SELECT AVG(SALARY) FROM EMP GROUP BY SALARY; 

Written below is a query to list the duplicate values in an Oracle table:-

SELECT NAME, COUNT (NAME) FROM EMPLOYEE GROUP BY NAME HAVING COUNT (NAME) > 1; 

The GRANT option in the IMP command can be used to import object grants.

The TRANSLATE function of Oracle is used for replacing a sequence of characters in a string with some other set of characters. The TRANSLATE function replaces a single character at a time. Let us take a look at an example of translating the string "ROLL41" to "RAMM42" with the help of the TRANSLATE function.

TRANSLATE("ROLL41", "OL1", "AM2");

The REPLACE function of Oracle is used for replacing a sequence of characters in a string with some other set of characters. Let us take a look at an example to translate the string "R12S121" to "R34S341" with the help of the REPLACE function.

REPLACE("R12S121", "12", "34");

Note that every occurrence of the substring "12" is replaced by the substring "34".

Recommended Resources

• SQL Interview Questions
• DBMS Interview Questions

There are two memory layers in the Oracle shared pool:-

• Library Cache - The information about the SQL statements that were parsed, data about cursors, and any plan data that might be present is present in the Library Cache.
• Data Dictionary Cache - The Data Dictionary Cache layer contains information about the accounts of the users, their privileges, and information about segments.

The different components of the physical database structure of an Oracle database are listed below:-

• Greater than equal to two redo log files.
• Greater than equal to one data file.
• Greater than equal to one control file.

The C language was used to develop the Oracle database.

The Oracle Database allocates logical space for all data in the database in addition to the physical files. The logical units of database space allocation are data blocks, extents, segments, and tablespaces. At a physical level, the data is stored in data files on a disk. The data in the data files are stored in operating system blocks.

There are two main components in the logical database structure of the Oracle database:-

1. Tablespaces: The basic storage allocation in an Oracle database is a tablespace. Each tablespace is composed of one or more physical (operating system) files. The SYSTEM tablespace is used to create each and every database. Other tablespaces are created by the Database Administrator.
2. Database's schema objects: A schema in Oracle is similar to an account or a username. Each object in the database is owned by a schema. Every Oracle database is created with two initial schemas: SYS, which is used to store the data dictionary, and SYSTEM, which often stores some data dictionary extensions as well as critical tables for other tools. Other schemas are created by the DBA. Each schema can be granted quotas in any tablespace.

The Logical Storage Unit of an Oracle database is called a tablespace. It is nothing but a set of related logical structures. Tablespace groups relate the logical structures of the database together. Logically, the data is stored in the tablespaces in Oracle and physically, the data is stored in the datafiles associated with the respective tablespaces.

The default tablespaces of Oracle are as follows:-

1. The SYSTEM and SYSAUX tablespaces - These store system-generated objects such as data dictionary tables in them. One should not store any object in these tablespaces.
2. The USERS tablespace - It is used for ad-hoc users.
3. The UNDOTBS1 tablespace - Is used for holding the undo data.
4. The TEMP tablespace - It is the temporary tablespace that is used for storing intermediate results of sorting, hashing, and large object processing operations.

If a tablespace is offline, we cannot access data stored in it. In contrast to that, if a tablespace is online, the data of the tablespace is available for reading as well as writing.

When any database is created in the Oracle database system, a SYSTEM tablespace is automatically generated. The Data dictionary tables for the entire database are present in The SYSTEM tablespace. It is important that the SYSTEM tablespace remains online always as it contains the data dictionary that must be available to Oracle.

An Oracle table is a basic unit of data storage in an Oracle database. Every accessible information of any user is present in rows and columns of an Oracle table.

Oracle uses snapshots, which are also known as materialized views, in order to replicate data to the non-master sites in a replicated environment. Snapshots are also used to cache the "expensive" queries in a data warehouse environment. So in short, a snapshot is nothing but a copy of the target master table from a single point in time.

The RAW datatype is used to store values in binary data format in an Oracle Database. The maximum size for a RAW datatype in a table is 32767 bytes.

Savepoints can be used to break a transaction into smaller parts. It also allows the rolling back of a transaction. At any given time, at most five save points are allowed. Savepoints save our data, and therefore, whenever we encounter an error, we can roll back to the point where we had saved our SAVEPOINT.

The description of various Oracle database objects is as follows:-

• Tables: Tables are a set of elements organized in a vertical and horizontal fashion.
• Tablespaces: Tablespaces are the logical storage unit in Oracle.
• Views: A view can be defined as a virtual table that has been derived from one or multiple tables.
• Indexes: Indexes are a performance-tuning method to process the records.
• Synonyms: Synonyms are names for tables.

The ANALYZE command in Oracle can be used to perform a number of functions on indexes, tables, or clusters. Some of the use cases of the ANALYZE command in Oracle are as follows:-

• The ANALYZE command can be used to find out migrated and chained rows of the table or cluster. Also, it can be used to validate the structure of the object.
• It helps in collecting the statistics about objects which the optimizer is using. After that, they are stored in the data dictionary.
• It helps in deleting statistics used by objects from the data dictionary.

A hash cluster provides an alternative to a non-clustered table with an index or an index cluster. Using indexed tables or index clusters, the Oracle Database is able to locate the rows in a table using key values that the database stores in a separate index.

The most common types of modules in Oracle forms are as follows:-

• Form module.
• Menu module.
• Pl/SQL Library module.
• Object Library module.

Synonyms are defined as aliases for tables, views, sequences or program units. There are two types of synonyms in the Oracle database:-

• Private Synonyms: These synonyms are only accessible to the owner.
• Public Synonyms: These synonyms are accessible to any database user.

The BLOB data type in the Oracle database has a varying length binary string. It is used to store two gigabytes of memory and for it, the length needs to be specified in bytes. An example to illustrate the usage of the BLOB data type is given below:-

Creating a table:-

create table photos(name varchar(32) not null primary key, picture blob(10M));

Querying for all logotype pictures:-

select name,length(picture) from photos where name like '%logo%';

The Logical backup mechanism is for reading a set of database records and writing them into a file. We can use an Export utility to take the backup while an Import utility can be used to recover from the backup.

We can define a recursive hint as to the number of times a dictionary table is continuously called by various processes. Recursive hints occur because of the small size of the data dictionary cache.

The biggest limitation of the CHECK constraint is as follows:- The condition needs to be a boolean expression that is being evaluated using the values in the row being inserted or updated. It can also not contain any subqueries whatsoever.

Now that we know all about the hiring process of Oracle, here are a few tips which you can use to crack Oracle’s interview and get a job:-

1. Have a good understanding of Java - Java programming language is one of Oracle’s most used products and therefore, it is recommended to know about Java in depth before the coding interview of Oracle. Also, knowing about frameworks of Java like Spring, etc and the SOLID principles of Object Oriented Design may be really helpful.
2. Be well versed with Data Structures and Algorithms - At Oracle, there is always an appreciation for good problem solvers. If you want to have a good impression on the interviewers, the best way is to prove that you have worked a lot on developing your logic structures and solving algorithmic problems. A good understanding of Data Structures and Algorithms and having one or two good projects always earn you brownie points with Oracle.
3. Use the STAR method to format your Response - STAR is an acronym for Situation, Task, Action, and Result. The STAR method is a structured way to respond to behavioral based interview questions. To answer a provided question using the STAR method, you start by describing the situation that was at hand, the Task which needed to be done, the action taken by you as a response to the Task, and finally the Result of the experience. It is important to think about all the details and recall everyone and everything that was involved in the situation. Let the interviewer know how much of an impact that experience had on your life and in the lives of all others who were involved. It is always a good practice to be prepared with a real-life story that you can describe using the STAR method.
4. Know and Describe your Strengths - Many people who interview at various companies, stay shy during the interviews and feel uncomfortable when they are asked to describe their strengths. Remember that if you do not show how good you are at the skills you know, no one will ever be able to know about the same and this might just cost you a lot. So it is okay to think about yourself and highlight your strengths properly and honestly as and when required.
5. Discuss with your interviewer and keep the conversation going - Remember that an interview is not a written exam and therefore even if you come up with the best of solutions for the given problems, it is not worth anything until and unless the interviewer understands what you are trying to say. Therefore, it is important to make the interviewer that he or she is also a part of the interview. Also, asking questions might always prove to be helpful during the interview.

There are around 3-4 Interview Rounds: Online Coding Round(One Round), Technical Round (2 Rounds), and HR Round.
 

There are a lot of high-quality products which Oracle employees work on every day and the amount of opportunity that Oracle presents its employees is humongous. Also, the work culture is really good over there and the compensation offered to Oracle employees is on the higher end of the standards of the Information Technology or Software Industry.

The toughness of an interview depends upon the amount of hard work you have put in to prepare for them. Usually, the questions asked in a standard Oracle interview are of Easy to Medium Level but it varies from person to person. Since the number of interview rounds range anywhere from four to seven, it can be intimidating at times for a candidate. But if you are in, it is going to be worth the effort.

It is always nice to ask questions about the company’s culture and what is the current technology using which the company makes its products. Asking about the future innovations at Oracle also might be a good idea as it might make the interviewer believe that you are looking forward to joining Oracle for a long time. You can also ask about the interviewer’s personal experience at Oracle and what skills you must develop before you join the job.

Some of the famous products of Oracle are as follows:-

1. Oracle Database
2. Oracle E-Business Suite
3. PeopleSoft Enterprise
4. Siebel
5. Oracle JDeveloper, a freeware IDE

As mentioned previously in this article, having a good knowledge of Java will definitely prove to be helpful to an Oracle developer. Also, having a thorough knowledge of SQL databases, cloud technologies and various models of software engineering, for instance, Agile Method, Waterfall Method, etc. might prove to be useful.

As is the case with any other software company, Oracle also looks forward to hiring people with extremely good problem-solving skills. Someone who is well-versed in Data Structures and Algorithms and can apply them in real-world problems will definitely have a good chance of getting hired at Oracle. Also, having a few good projects, preferably using Java and its frameworks like Spring, etc. also might increase the chance of one getting hired at Oracle.