Database Interview Questions and Answers in 2025 (100+ Q&A)

Database

Ques:- what are different types of datasets? what are different characteristics or properties of those datasets? what are the advantages and disadvantages of each dataset on each other?

Asked In :- MedCords, Zentech, Inc, first derivatives, iex,

Right Answer:
There are several types of datasets, including:

1. **Structured Datasets**
- **Characteristics**: Organized in a fixed format (e.g., tables with rows and columns), easily searchable.
- **Advantages**: Easy to enter, query, and analyze using SQL; efficient storage.
- **Disadvantages**: Limited flexibility; not suitable for unstructured data.

2. **Unstructured Datasets**
- **Characteristics**: No predefined format (e.g., text, images, videos).
- **Advantages**: Can store a wide variety of data types; more flexible.
- **Disadvantages**: Difficult to analyze and query; requires advanced processing techniques.

3. **Semi-Structured Datasets**
- **Characteristics**: Contains both structured and unstructured elements (e.g., JSON, XML).
- **Advantages**: Flexible structure; can represent complex data relationships.
- **Disadvantages**: More complex to process than structured data;

Comments

Admin May 17, 2020

unfortunately, I am a beginner. I have just started learning about datasets. please give me the reply as soon as possible. It will useful for my academics. Thank you in advance. Hope I will get the best reply.

Database

Ques:- Explain about ur projets on teradata???

Asked In :-

Right Answer:
In my projects on Teradata, I focused on data warehousing and analytics. I designed and implemented ETL processes to extract data from various sources, transformed it for analysis, and loaded it into Teradata. I utilized SQL for querying large datasets, optimized performance through indexing and partitioning, and created reports and dashboards for business insights. Additionally, I worked on data modeling to ensure efficient storage and retrieval of information.

Database

Ques:- First input columns brand, mt, re values are ov, 1,re vg, 2,re wu ,3,re. Second input columns are brand, mt, cx their records are ov,4,vg ,5,cx Wu, 6,cx and third input columns brand, mt, rt values are ov,7,rt vg, 8,rt wu, 9,rt but my output is brand, re, cx,rt values are ov, 1,4,7 vg, 2,5,8 wu, 3,6,9

Asked In :-

Right Answer:
To achieve the desired output, you need to perform a join operation on the three input tables based on the "brand" and "mt" columns. The output should combine the values from each table into a single row for each matching brand and mt combination, resulting in the following output:

```
brand | re | cx | rt
---------------------
ov | 1 | 4 | 7
vg | 2 | 5 | 8
wu | 3 | 6 | 9
```

Database

Ques:- .dbf file corrupted Dear Friends, I am using DBF file in Foxpro. DBF file corrupt and show message “Not a database file” Waiting for your reply. With regards!

Asked In :- Telesoft Labs,

Database

Ques:- Source File: Target EMPNO, SAL Empno, Format 101, 1000 101, 1000 101, 1100 101, 1000, 1100 101, 1000 101, 1000, 1100, 1000 101, 10000 101, 1000, 1100, 1000, 10000 102, 1100 102, 1100 102, 1300 102, 1100, 1300 102, 1200 102, 1100, 1300, 1200 102, 1500 102, 1100, 1300, 1200, 1500 How can i get that output using datastage(ETL) tool

Asked In :- NeoGrowth Credit, HummingWave Technologies, vas,

Right Answer:
To achieve the desired output in DataStage, you can follow these steps:

1. **Create a Job**: Start a new DataStage job.
2. **Source Stage**: Use a Sequential File stage to read the input data.
3. **Transformer Stage**: Add a Transformer stage to process the data.
- Use an aggregation function to concatenate the SAL values for each unique EMPNO.
4. **Output Stage**: Use a Sequential File or Database stage to write the output data.
5. **Link Stages**: Connect the stages appropriately to ensure data flows from the source to the output.

Make sure to configure the stages correctly to handle the data format and aggregation as required.

Database

Ques:- query to Compare data of two tables between two different Databases(Oracle and SQL Server) Eg., Source Database: Oracle Table: Employee Target Database : SQL Server Table : emp

Asked In :- kpoint technologies,

Right Answer:
To compare data between an Oracle table and a SQL Server table, you can use a tool like SQL Server Integration Services (SSIS) or write a script in a programming language that can connect to both databases. Here's a simple SQL-like pseudocode example:

1. **Extract data from Oracle:**
```sql
SELECT * FROM Employee@oracle_db_link;
```

2. **Extract data from SQL Server:**
```sql
SELECT * FROM emp;
```

3. **Compare the results in your application logic:**
- Load both datasets into memory and compare them using your preferred programming language (e.g., Python, Java, etc.).

Alternatively, if you want to do it directly in SQL, you would need to use a database link or a middleware that allows cross-database queries, which is not natively supported between Oracle and SQL Server.

Database

Ques:- I have single column in a file. Input 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 my output is file 1 have 1,2,3,10,11,12 file 2 have 4,5,6,13,14,15 and file 3 have 7,8,9 how is it possible in datastage

Asked In :-

Right Answer:
You can achieve this in DataStage by using a combination of the "Transformer" stage and the "Filter" stage.

1. Use a "Sequential File" stage to read the input file.
2. Add a "Transformer" stage to assign a group number based on the row number. For example:
- Group 1: Rows 1-3 and 10-12
- Group 2: Rows 4-6 and 13-15
- Group 3: Rows 7-9
3. Use a "Filter" stage to separate the records into three different outputs based on the group number.
4. Write the outputs to three different "Sequential File" stages for each file.

This way, you can direct the specified rows into their respective output files.

Database

Ques:- give a simple example of physical and logical data independence

Asked In :-

Database

Ques:- Design an ETL process( batch job/script)from source to starting that u will not be dependent on the source in the near future?please elobarate details on what are things to consider.if you’d like to do a diagram that will be great.please answer it

Asked In :- 159 Solutions, Discovery, Inc,

Database

Ques:- Data structure used to implements a menu:

Asked In :- Numeric Technologies (IL),

Right Answer:
A tree data structure is commonly used to implement a menu.

Database

Ques:- How default key is different from primary key?

Asked In :- EPFO, HeapTrace, tejas networks,

Right Answer:
A primary key uniquely identifies each record in a table and cannot contain null values, while a default key (often referred to as a default constraint) provides a default value for a column when no value is specified, but it does not enforce uniqueness.

Database

Ques:- what is tkprof tool and how it is used???

Asked In :- OneOrigin,

Right Answer:
Tkprof is a performance analysis tool for Oracle databases that formats the output of SQL trace files. It helps developers and database administrators understand the performance of SQL queries by providing a detailed report of execution times, resource usage, and wait events. To use it, you generate a trace file using the SQL TRACE feature, then run the tkprof command on that trace file to produce a readable report.

Database

Ques:- What is the difference between specialization and generalization?

Asked In :-

Database

Ques:- What is a sequence? Explain it with one example?

Asked In :- CakeSoft Technologies, Athena Global Technologies,

Database

Ques:- What is the candidate key used for?

Asked In :- icims,

Database

Ques:- What is the difference between primary and candidate key?

Asked In :- ncis,

Database

Ques:- What does specialization in DBMS mean?

Asked In :- ITRS Group, ananth technologies, dwp digital, Dextris Infoservices,

Database

Ques:- What is the function of cluster index?

Asked In :- Versant Online Solutions, data domain, ginkgo bioworks, inc., housecall pro,

Database

Ques:- How concurrency problems effect the database?

Asked In :- Mirraw, codeworks,

Database

Ques:- How does non-cluster index functions?

Asked In :- the cheesecake factory, first derivatives, vectra ai,

Database is the backbone of almost every modern application, enabling structured storage, retrieval, and management of data. Whether it’s a simple website or an enterprise-grade system, databases play a critical role in ensuring data integrity, availability, and scalability. Understanding database fundamentals is crucial for a variety of IT roles including backend developers, data analysts, system architects, and DBAs (Database Administrators).

This category focuses on key database concepts like relational and non-relational databases, data models, normalization, SQL queries, indexing, transactions, and ACID properties. It also covers real-time use of major database systems like MySQL, Oracle, SQL Server, PostgreSQL, and NoSQL solutions like MongoDB and Cassandra.

In interviews, candidates are often tested on query optimization, joins, subqueries, stored procedures, data security, and performance tuning techniques. With the rise of data-driven decision-making, even non-developers are expected to understand basic SQL and database reporting tools.

At Takluu, we provide curated resources, commonly asked interview questions, real-world scenarios, and sample queries to help you prepare better. We simplify complex topics with clear explanations and guide you on how to handle database-related problem-solving questions with confidence.

Whether you’re aiming to work in software development, data science, business intelligence, or IT infrastructure, having a strong foundation in databases gives you a significant edge. Our content is tailored to align with current industry expectations and real interview patterns.

Master the art of storing and managing data — because in today’s tech landscape, data is power, and databases are where that power resides.

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