This blog offers sample SQL interview questions and answers for both freshers and experienced candidates, covering topics like MySQL databases and MS SQL Server. It is a comprehensive tool that allows you to get the most out of your benefits and makes Interview preparation simple. View the most popular MS SQL Interview questions and answers. Enroll in our MS SQL Server training in Chennai at Softlogic Systems.
1. What does “database” mean to you?
A database is an organized type of data storage that allows for effective management and retrieval of data. It is a group of tables that contain the data arranged for easy access. Tables are made up of rows and columns, where the rows are referred to as attributes and the columns as records or tuples. A couple of examples of databases are the Bank Management Database and the University Management Database.
2. What does RDBMS mean to you?
Relational Database Management System is all that RDBMS stands for. It’s the software that makes it possible to manage, retrieve, query, and save data from relational databases. Along with interacting with users and the database, RDBMS is also capable of performing administration duties, including controlling data storage, granting access to data, and evaluating database performance.
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3. Which are the various SQL subsets?
Data Definition Language (DDL): This language lets you work with databases to create, modify, and delete items, among other things.
Data Manipulation Language (DML): Data access and manipulation are made possible using it. It facilitates the insertion, updating, deleting, and retrieval of database data.
Data Control Language (DCL): You can manage database access with it. Grant and revoke access permissions, for instance.
4. What does the term “SQL Server Agent” mean to you?
A Windows service called SQL Server Agent is used to plan and carry out tasks. In this case, a task is contained in each step, and each job comprises one or more steps. As a result, the server agent uses the SQL Server to store job data and carry out work according to a set schedule. The SQL Server Agent’s primary parts are jobs, schedules, operators, and alerts.
Example: You may easily automate this activity to enable the schedule to occur on its own, for example, if an organization wants to take a backup of the firm servers every day at 7:00 p.m. If an error occurs during the backup process, the SQL Server Agent logs the incident and alerts the relevant team. Explore the primary key and foreign key in SQL.
5. Explain the various SQL Server authentication methods.
The database engine is configured with the authentication mechanism specified. The following are some of the many authentication methods that SQL Server offers:
Windows Authentication Mode: Using a Windows account, you can connect to the server using the Windows Authentication Mode. In this case, the server retrieves the computer’s login and password for authentication. In this option, the SQL server authentication mode is also disabled.
Mixed mode: This connection method allows you to utilize Windows authentication or SQL Server authentication to connect to an SQL Server instance. In this mode, the user configures the database’s login and password.
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6. What commands are MINUS, INTERSECT, and UNION?
The results of two tables can be combined and duplicate entries can be eliminated using the UNION operator.
Rows from the first query can be returned using the MINUS operator, but rows from the second query cannot.
The outcomes of both searches are combined into a single row using the INTERSECT operator.
A few prerequisites must be met before executing either of the aforementioned SQL statements:
- Every SELECT query inside the clause needs to contain an equal number of columns.
- Additionally, the data types in the columns need to be the same.
- The columns need to appear in the same order in every SELECT statement.
7. OLTP: What is it?
Large groups of people may conduct enormous numbers of database transactions in real-time, usually via the Internet, thanks to OLTP, or online transactional processing. Any time data is updated, added, removed, or queried in a database, a database transaction takes place.
8. Define Inner Join with an example
The entries in the join tables that have matching values are retrieved using an inner join. Based on a relevant column, it merges rows from two tables and returns only the matched record. Query joins are the main use for the inner join.
SELECT *
FROM Table_A
JOIN Table_B;
SELECT *
FROM Table_A
INNER JOIN Table_B;
9. Describe SQL Server and list its essential parts.
SQL Server is one RDBMS that Microsoft created. The two primary components are SQLOS and the database engine. Database files, pages, indexes, and query processing can all be handled by the database engine’s relation engine. Moreover, SQLOS is nothing more than a SQL operating system. Operating systems like storage and I/O management are provided by SQLOS. It also manages synchronization services and exception handling, among other things.
10. What do the terms “ACID properties” mean?
All that remains of the ACID characteristics are atomicity, consistency, isolation, and durability. In general, every transaction needs to adhere to ACID characteristics.
Atomicity: It guarantees that a transaction must be executed in its entirety in a single execution. If a transaction merely consists of a subset of operations, the goal of the transaction may be compromised. However, atomicity rules out this scenario.
Consistency: It guarantees perfect data consistency both before and after a transaction is completed. To put it plainly, transactions shouldn’t jeopardize data consistency.
Isolation: It guarantees total separation between each transaction and other transactions. It implies that every transaction in the system needs to operate as though it is the only one taking place.
Durability: It guarantees that each transaction can be recovered when necessary. Once a transaction is committed, all updated data has been made in the database and is available for users to retrieve at any time.
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11. What does SQL Server Subquery mean?
When a query is nested inside a statement, such as SELECT, INSERT, UPDATE, or DELETE, it is referred to as a subquery. In addition, a sub-query is a query that is nested inside another sub-query. Moreover, an inner query or an inner select are other names for a subquery. In the same vein, the statement containing the subquery is referred to as an outer select or query.
12. Which SQL Server subqueries are there?
Here are several sorts of subqueries:
Table aliasing subqueries
- Subqueries utilizing NOTIN and IN
- Subqueries in the commands UPDATE, DELETE and INSERT
- Subqueries, including comparative remarks
- Modified comparison operators by ALL, SOME, or ANY
- Subqueries with and without existing data
13. What are triggers in the SQL server, and what kinds of triggers are there?
The unique stored routines are called triggers. Triggers will execute automatically on the SQL server whenever there is an event. Triggers come in three varieties: LOGON, DDL, and DML.
LOGON Triggers: When a user creates a LOGON event, LOGON triggers are triggered.
DDL Triggers: When a Data Definition Language (DDL) event occurs, it is triggered.
DML Triggers: They are activated whenever Data Manipulation Language (DML) modifies data.
14. When is it possible to use SQL Server triggers?
- When a database’s activity audit trail becomes necessary
- Obtaining more information that isn’t contained in a database
- To maintain referential integrity
- To put a business rule into action
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15. A Sparse Column: What Is It?
Simply put, sparse columns are regular table columns with optimal storage for NULL data. They cut the amount of space needed for NULL values by roughly 20–40%. Filtered indexes and column sets can be utilized with sparse columns. The CREATE TABLE and ALTER TABLE statements define sparse columns.
16. What does the term “check constraints” mean?
Values can be limited with the aid of check constraints to preserve domain integrity. You can employ logical operators, for example, that only return true or false. They can be applied to limit the maximum and lower values within a range by establishing a check constraint. In the same way that you may apply a single constraint to many columns, you can also apply multiple check constraints to a single column.
17. How is data from an SQL table selected?
The SELECT command facilitates the process of selecting data from databases. The SELECT command is used in the example below to retrieve all of the data from a table.
SELECT *
FROM DimEmployee
ORDER BY LastName;
If you need to choose a subset of a table, you must use the WHERE clause in addition to the SELECT query to get the information you need. The meaning of the WHERE clause in a SELECT statement is illustrated in the example below.
SELECT FirstName, LastName, StartDate AS FirstDay
FROM DimEmployee
WHERE EndDate IS NOT NULL
AND MaritalStatus=’M’
ORDER BY LastName;
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Bottom Line
In this article, we have addressed the majority of commonly asked MS SQL Interview questions and answers. We hope that reading this article helped you grasp the fundamental ideas behind SQL servers. Enroll in our MS SQL Server training in Chennai and accelerate your career.
