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

sql

Ques:- i need to store decimal places but am not worried about rounding errors. what would be a goaod data type to use ?

Asked In :- PureSoftware, Chella Software, G S Lab, Pennant Technologies, Talentica, Graphene, DCM Shriram, O Clock Software, C-Square Info Solutions, Turing Analytics,

Comments

Archand Sep 22, 2020

byte is exactly what you need

Database Administrator (dba) SQL Server

Ques:- What is DYNAMIC SQL method ?

Asked In :- Pi Techniques, CitiusTech Healthcare Technology, Qualminds Technologies, Testbook, MSys Technologies, Tekskills, Quantified Commerce, Valuefy Solutions, iFAST Corporation, 4W,

Right Answer:
Dynamic SQL is a programming technique that allows you to construct and execute SQL statements at runtime, rather than hardcoding them in your application. It enables the creation of flexible and adaptable queries by using variables and concatenating strings to form SQL commands.

Database Administrator (dba) SQL Server

Ques:- In a Distributed Database System Can we execute two queries simultaneously ? Justify ?

Asked In :- Bit Canny Technologies, Tatvic Analytics, Testrig Technologies, C-Edge Technologies, Vofox Solutions, SEEBURGER, Ulearn, Emma, Agaram InfoTech, ActiveLobby,

Right Answer:
Yes, in a Distributed Database System, we can execute two queries simultaneously. This is possible because distributed databases can handle multiple transactions concurrently across different nodes, allowing for parallel processing of queries.

SQL Server Web Designer

Ques:- What is an Exception ? What are types of Exception ?

Asked In :- CTRLS DATACENTERS, bKash, Data Patterns, Webtech Developers, Cinif Technologies, Gallagher Offshore, MyDBOPS, Cateina Technologies, Icon Technologies, Techvaria Solutions,

Right Answer:
An exception is an event that occurs during the execution of a program that disrupts the normal flow of instructions. The types of exceptions include:

1. **Checked Exceptions**: These are exceptions that are checked at compile-time, such as `IOException` or `SQLException`.
2. **Unchecked Exceptions**: These are exceptions that occur at runtime and are not checked at compile-time, such as `NullPointerException` or `ArrayIndexOutOfBoundsException`.
3. **Errors**: These are serious issues that a typical application should not try to catch, such as `OutOfMemoryError` or `StackOverflowError`.

Database Administrator (dba) SQL Server

Ques:- How a sql server is been used in our programs?

Asked In :- Circle Internet Financial, Comviva, Tripod Technologies, SpeedLabs, Silicon Stack, Smart Sight Innovations, Appzone, MQL, Discovery, Inc, cigniti technologies,

Right Answer:
SQL Server is used in programs to store, retrieve, and manage data through SQL queries. Applications connect to the SQL Server database using connection strings, allowing them to execute commands like SELECT, INSERT, UPDATE, and DELETE to manipulate data as needed.

Database Architect/ Designer SQL Server

Ques:- Explain Normalization and Denormalization with examples.

Asked In :- Amrut Software, Grid Logic Software, Evolvus Solutions, Techversant Infotech, CitiusTech Healthcare Technology, SRF, Siam Computing, MagicPin, Sigmoid Analytics, Health Prime Services (India),

Right Answer:
Normalization is the process of organizing a database to reduce redundancy and improve data integrity. It involves dividing large tables into smaller, related tables and defining relationships between them. For example, instead of having a single table for customers and their orders, you might have one table for customers and another for orders, linked by a customer ID.

Denormalization is the process of combining tables to improve read performance at the cost of increased redundancy. For example, you might combine the customers and orders tables into one table that includes customer details with each order, making it faster to retrieve all information in a single query, but increasing the risk of data inconsistency.

Data Warehouse Developer SQL Server

Ques:- What does the Log Reader agent in SQL Server 2005 replication do?

Asked In :- DecisionTree Analytics and Services, Smart Cube India, Innodata, Mind Infotech, Graphene, TechMojo Solutions, Smart Joules, SmartPoint Technologies, Melio Systems, Statista,

Right Answer:
The Log Reader agent in SQL Server 2005 replication reads the transaction log of the published database to identify and capture changes (inserts, updates, deletes) that need to be replicated to the subscribers.

Data Warehouse Developer SQL Server

Ques:- What are the three possible functions of the plus (+) operator in SQL Server 2005, the base installed T-SQL?

Asked In :- TNQ Technologies, Novalnet e-Solutions, XBRL Ultima, Anand Rathi, Indium Software, Envision Financial Systems India, Samsung R&D Institute India, Cavisson Systems, 3clogic, Smart Soc Solutions,

Right Answer:
The plus (+) operator in SQL Server 2005 can function as:

1. Arithmetic addition for numeric values.
2. String concatenation for character strings.
3. A way to indicate outer joins in certain join syntax (though this usage is deprecated).

Database Analyst/ Programmer SQL Server

Ques:- What magic tableWhat happen when we run any command or stored procedure is it compile ?

Asked In :- Sumedha Softech, Zyoin Web Pvt., PreludeSys India, Talencia LLC, Statestreet HCL Services, OSI Digital, Iprimed Education Solutions, Spericorn, M3bi, Celigo,

Right Answer:
A magic table in SQL Server refers to the special tables created by the system during the execution of triggers. When a trigger is fired, SQL Server creates a copy of the affected rows in these magic tables, named inserted and deleted, allowing you to access the new and old values of the rows being modified.

When you run any command or stored procedure, it is compiled into an execution plan before being executed. This compilation process optimizes the query for performance.

Database Architect/ Designer SQL Server

Ques:- What is the use of database index (apart from fast searching of records);What is use of composite key ?

Asked In :- Coviam Technologies, CTRLS DATACENTERS, i-exceed technology solutions, ANR Software, Sarjen Systems, RORO, Neustar, Datagrokr, Baryons Software Solutions, Department for Transport,

Right Answer:
A database index improves the performance of queries by allowing faster access to rows, reduces the amount of data that needs to be scanned, and can enforce uniqueness. A composite key is used to uniquely identify a record using two or more columns, which helps maintain data integrity and allows for more complex relationships between tables.

Database Architect/ Designer SQL Server

Ques:- How to replace particular string.For example:- suppose their are 1000 of records for email-id.like tarun.it@hotmail.com..but i want to replace the only hotmail.com for all email-ids not the user name(tarun.it) with yahoo.com.

Asked In :- Trigent Software, Evolvus Solutions, Novatech Software, Solix Technologies, Inc, TriSys, Infomats Technologies, JSL, ImpactQA, Netcon Technologies, VEDA IIT,

Right Answer:
You can use the `REPLACE` function in SQL Server to replace "hotmail.com" with "yahoo.com" in the email addresses. Here’s the SQL query:

```sql
UPDATE your_table_name
SET email_column = REPLACE(email_column, 'hotmail.com', 'yahoo.com')
WHERE email_column LIKE '%hotmail.com';
```

Project Leader/ Project Manager SQL Server

Ques:- What is table in SQL server? What is ##table in SQL server?

Asked In :- Shipmnts, e2e, Sanitation Districts of Los Angeles County, Softeon India, Tecnotree, Health Prime Services (India), Planet Spark, Mitsogo Technologies, TranzINDIA, Sanfoundry,

Right Answer:
A table in SQL Server is a structured collection of data organized in rows and columns, where each row represents a record and each column represents a field of that record.

A `##table` in SQL Server is a global temporary table, which is accessible to any session and exists until all sessions referencing it are closed.

Data Warehouse Developer SQL Server

Ques:- What is a transaction isolation level and What is the advantage of it? What are different options that we set for a transaction isolation level? Transaction isolation levels are used when we go for transactions in stored procedures used in Transact SQL.

Asked In :- Energytech Global, Destination technologies, Zorba Consulting, Ideas2IT, Bizacuity Solutions, VBeyond, Polus Software, Sara Analytics, Qualitrix, LogBase Technologies,

Right Answer:
A transaction isolation level defines the degree to which the operations in one transaction are isolated from those in other concurrent transactions. The advantages include controlling data consistency and preventing issues like dirty reads, non-repeatable reads, and phantom reads.

The different options for transaction isolation levels in SQL Server are:

1. **Read Uncommitted**: Allows dirty reads.
2. **Read Committed**: Prevents dirty reads; only committed data is read.
3. **Repeatable Read**: Prevents dirty reads and non-repeatable reads; ensures that if a row is read twice, it will return the same data.
4. **Serializable**: Prevents dirty reads, non-repeatable reads, and phantom reads; ensures complete isolation by locking the range of rows.
5. **Snapshot**: Provides a view of the data as it was at the start of the transaction, preventing locks and allowing for consistent reads.

Project Leader/ Project Manager SQL Server

Ques:- How we can make sure that the SQL query does not return NULL values?

Asked In :- Elite Software Solutions, scandid, POPCORNAPPS SOFTWARE PVT, Mundrisoft Solutions LLP, Chella Software, CrimsonLogic India, Mazenet Solution, Vinove Software and Services, Spericorn, Advantage Club,

Right Answer:
You can ensure that the SQL query does not return NULL values by using the `WHERE` clause with conditions that filter out NULLs, such as `WHERE column_name IS NOT NULL`, or by using the `COALESCE` function to replace NULLs with a default value.

Project Leader/ Project Manager SQL Server

Ques:- What is the difference between User Identification and Authentication?

Asked In :- Xoriant Solutions Pvt Ltd, Priya Softweb Solutions, LiteBreeze Infotech, Shore Infotech India, XBRL Ultima, Chella Software, NAL, Tessolve, Unilogic Software, Yalamanchili Software,

Right Answer:
User identification is the process of recognizing a user by their unique identifier, such as a username or ID. Authentication, on the other hand, is the process of verifying that the user is who they claim to be, typically through a password or other credentials.

Data Warehouse Developer SQL Server

Ques:- Provide all the built in string function of SQL SERVER

Asked In :- LiteBreeze Infotech, EdgeVerve Systems, FUTURISM TECHNOLOGIES PVT, Ramboll India, Gainers Infotech, WebMobril Technologies, Streebo Solutions, Sterling Software (India), Analyttica Datalab, Kendo,

Right Answer:
Here are the built-in string functions in SQL Server:

1. LEN()
2. DATALENGTH()
3. UPPER()
4. LOWER()
5. SUBSTRING()
6. CHARINDEX()
7. REPLACE()
8. RTRIM()
9. LTRIM()
10. CONCAT()
11. LEFT()
12. RIGHT()
13. FORMAT()
14. STUFF()
15. REVERSE()
16. SPACE()
17. STRING_AGG() (SQL Server 2017 and later)
18. PATINDEX()
19. NCHAR()
20. CHAR()

These functions can be used for various string manipulations and operations.

Database Architect/ Designer SQL Server

Ques:- What cursor type do you use to retrieve multiple record sets?

Asked In :- iROID Technologies, Anand Rathi IT, ANR Software, Saraca Solutions, UCA, Vinculum Solutions, Capital Numbers, Microverse Automation, L Cube Innovative Solutions, Relinns Technologies,

Right Answer:
Use a "forward-only" or "static" cursor type to retrieve multiple record sets.

Database Architect/ Designer SQL Server

Ques:- What is a VIEW? How to get script for a view?

Asked In :- Sumedha Softech, Qualminds Technologies, FIN Infocom, Softeon India, Shadowfax Technologies, KSB Tech, Polus Software, Thryve Digital, Busy Infotech, RWE Supply & Trading,

Right Answer:
A VIEW is a virtual table in SQL that is based on the result of a SELECT query. It does not store data itself but provides a way to present data from one or more tables in a specific format.

To get the script for a view in SQL Server, you can use the following command:

```sql
EXEC sp_helptext 'view_name';
```

Replace `view_name` with the name of the view you want to script.

Database Architect/ Designer SQL Server

Ques:- What is data base system? What is dbms? Give the difference between that and give the information about data base catalog?

Asked In :- Recodem, SRS Business Solutions (India), G S Lab, Nohitatu, Narola Infotech, Ideas2IT, 3clogic, Yagna iQ, Sankey Solutions, Knot Solutions,

Right Answer:
A database system is a collection of software and hardware components that manage and store data, allowing users to create, retrieve, update, and delete data efficiently. A Database Management System (DBMS) is software that facilitates the creation, manipulation, and administration of databases.

**Differences:**
- A database system includes the DBMS along with the data itself and the hardware, while a DBMS is just the software component.
- The database system encompasses the entire environment for data management, whereas the DBMS focuses on the management of the data.

A database catalog is a set of metadata that describes the structure of the database, including information about tables, columns, data types, constraints, and relationships between tables. It acts as a reference for the DBMS to manage the data effectively.

Project Leader/ Project Manager SQL Server

Ques:- Explain real time situation where you would use clustered and Non-clustered Indexes?

Asked In :- BillDesk, Systematix Infotech, SDL, District Cooperative Central Bank DCCB, RORO, Intelizign, Deep Compute, Interview Mocha, Konnect Insights, Paxcom,

Right Answer:
In a real-time situation, you would use a clustered index for a primary key column in a large table where you frequently query ranges of data, such as retrieving all orders within a specific date range. This is because a clustered index sorts and stores the data rows in the table based on the indexed column, improving the performance of range queries.

On the other hand, you would use a non-clustered index for columns that are frequently searched but not part of the primary key, such as a customer name or email address. This allows for faster lookups without affecting the physical order of the data in the table.

SQL, or Structured Query Language, is the essential tool for anyone working with relational databases. It serves as the universal language for interacting with these databases, allowing users to organize, retrieve, and manage vast amounts of data effectively. Developed in the 1970s, SQL has become the standardized method for database communication across a wide range of applications, from small business systems to enterprise-level data warehouses.

The power of SQL lies in its declarative nature. Instead of telling the computer how to find data, you simply tell it what data you want. This is done through a concise set of commands, such as SELECT to retrieve data, INSERT to add new records, UPDATE to modify existing records, and DELETE to remove them. These commands, often combined with clauses like WHERE to filter data and JOIN to link tables, enable complex data operations with relatively simple statements. For example, a single query can retrieve a list of all customers from a specific city, calculate their total spending, and sort the results by name.

SQL is a foundational technology for data science, business intelligence, and web development. It is used to query databases that power everything from social media platforms to banking systems. Its reliability, efficiency, and widespread adoption make it an indispensable skill for database administrators, developers, and data analysts. Mastering SQL provides the ability to unlock insights from data, maintain data integrity, and build robust, data-driven applications.

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