60+ SQL Database Administrator Interview Questions and Answers

A database management system (DBMS) is a software that manages and organizes databases. Primary key uniquely identifies a record, while foreign key establishes a relationship between tables.

• A DBMS is a software that allows users to create, manage, and manipulate databases.

• It provides tools for creating, modifying, and deleting databases, tables, and records.

• Primary key is a unique identifier for a record in a table.

• Foreign key establishes a relationship between two tables by ...read more

Composite key is made up of multiple columns while non-composite key is made up of a single column. Primary key can also be defined using unique, not null, or candidate key.

• Composite key uses multiple columns to uniquely identify a row while non-composite key uses a single column

• Primary key can be defined using unique, not null, or candidate key instead of explicitly defining it

• Candidate key is a unique key that can be used as a primary key

The question is about SQL Database Administration and covers various topics such as user management, job creation, query optimization, replication, troubleshooting, and backup/restore processes.

• To create new users/login, use the CREATE LOGIN and CREATE USER statements.

• To create a new job, use the SQL Server Agent or SQL Server Management Studio (SSMS).

• Log shipping involves jobs like backup, copy, and restore. Replication involves jobs like snapshot, log reader, and distributi...read more

I prefer SQL as it is the language of databases and allows for efficient data management.

• SQL is specifically designed for managing and querying databases

• It allows for efficient data retrieval and manipulation

• Other programming languages can be used in conjunction with SQL for more complex tasks

• Examples of other languages commonly used with SQL include Python and Java

Questions on SQL Database Administration including recursive stored procedures, optimization, recovery and backup, loading JSON files, scheduling, and cursor examples.

• For recursive stored procedures, use common table expressions (CTEs) to simplify the code

• Optimization techniques include indexing, query tuning, and partitioning

• Regular backups and testing of recovery procedures are essential for data protection

• To load JSON files in SQL, use OPENROWSET or BULK INSERT

• Scheduling c...read more

Clustered index determines the physical order of data in a table, while non-clustered index is a separate structure.

• Clustered index sorts and stores the data rows in the table based on their key values.

• Non-clustered index creates a separate structure that contains the key values and a pointer to the data row.

• A table can have only one clustered index, but multiple non-clustered indexes.

• Clustered index is faster for retrieving large amounts of data, while non-clustered index is...read more

Minimum memory configuration is used to allocate the minimum amount of memory required for SQL Server to run.

• Minimum memory configuration is used to ensure that SQL Server has enough memory to function properly.

• It is important to set the minimum memory configuration to a value that is appropriate for the workload of the server.

• If the minimum memory configuration is set too low, SQL Server may experience performance issues.

• For example, if a server has 16GB of RAM and the minim...read more

An end-to-end approach for data involves collection, processing, analysis, and reporting to derive insights.

• Data Collection: Gather data from various sources like databases, APIs, or user inputs.

• Data Cleaning: Remove duplicates and correct errors to ensure data quality.

• Data Transformation: Convert data into a suitable format for analysis, e.g., normalizing or aggregating.

• Data Analysis: Use SQL queries to extract insights, e.g., SELECT statements for reporting.

• Data Visualizati...read more

I prioritize issues based on impact, urgency, and complexity.

• Assess the impact of each issue on the system or users

• Consider the urgency of resolving each issue

• Evaluate the complexity of fixing each issue

• Prioritize critical issues that have high impact, urgency, and low complexity

• Create a priority list based on these factors

Joins in SQL are used to combine rows from two or more tables based on a related column between them.

• Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN.

• INNER JOIN returns rows when there is at least one match in both tables.

• LEFT JOIN returns all rows from the left table and the matched rows from the right table.

• RIGHT JOIN returns all rows from the right table and the matched rows from the left table.

• FULL JOIN returns rows when there is a match in one of t...read more

Resolved a critical database outage during peak hours by quickly identifying the root cause and implementing a fix.

• Identified the issue: A sudden spike in database connections caused a performance bottleneck.

• Analyzed logs: Reviewed error logs to pinpoint the source of the connection overload.

• Implemented a temporary fix: Increased the maximum connections limit to alleviate immediate pressure.

• Communicated with the team: Informed stakeholders about the issue and the steps being ...read more

Replication types and jobs, and how transactional replication works

• Replication types include snapshot, transactional, and merge

• Snapshot replication copies the entire database at a specific point in time

• Transactional replication copies changes as they occur

• Merge replication combines changes from multiple sources

• Transactional replication uses a distributor to send changes to subscribers

• Important jobs for transactional replication include the Log Reader Agent and Distribution Ag...read more

SQL is a relational database management system used to manage and store data.

• SQL stands for Structured Query Language

• Versions include SQL Server 2019, 2017, 2016, etc.

• To install SQL Server, download the installation file from Microsoft's website

• Run the installation file and follow the prompts to complete the installation process

Implementing robust security measures is essential to protect sensitive data in databases from breaches.

• Use encryption for sensitive data both at rest and in transit (e.g., AES for data at rest).

• Implement role-based access control (RBAC) to restrict data access based on user roles.

• Regularly update and patch database systems to protect against vulnerabilities.

• Conduct regular security audits and vulnerability assessments to identify and mitigate risks.

• Utilize firewalls and intr...read more

System databases are the default databases created during SQL Server installation.

• System databases include master, model, msdb, and tempdb.

• Master database stores system-level information.

• Model database is used as a template for new databases.

• Msdb database is used for SQL Server Agent and maintenance plans.

• Tempdb database is used for temporary storage of data.

• System databases cannot be deleted or detached.

• Additional system databases may be created by third-party software.

• Syste...read more

HA (High Availability) and DR (Disaster Recovery) ensure data accessibility and recovery in case of failures.

• High Availability (HA) ensures minimal downtime, e.g., SQL Server Always On Availability Groups.

• Disaster Recovery (DR) involves strategies to recover data after catastrophic events, e.g., backups and offsite replication.

• Types of HA include Clustering, Database Mirroring, and Replication.

• Types of DR include Full Backups, Log Shipping, and Geo-Replication.

• In case of AG f...read more

I prioritize tasks, set clear expectations, utilize time management tools, and communicate effectively.

• Prioritize tasks based on urgency and importance

• Set clear expectations with clients regarding response times and availability

• Utilize time management tools such as calendars and task lists

• Communicate effectively with clients to provide updates and manage expectations

Joins in SQL are used to combine data from two or more tables based on a related column.

• Joins are used to retrieve data from multiple tables in a single query.

• There are different types of joins such as inner join, left join, right join, and full outer join.

• The join condition is specified using the ON keyword and the related columns.

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column;

• Joins can be used to combine data from more than two tables as we...read more

Synchronization in Java is a process of controlling access to shared resources by multiple threads.

• Synchronization is achieved using synchronized keyword or locks.

• It prevents race conditions and ensures thread safety.

• Example: synchronized methods, synchronized blocks, ReentrantLock.

• Synchronization can cause performance issues if not used properly.

SQL editions are different versions of SQL Server with varying features and capabilities.

• SQL Server Express - free, limited to 10GB database size

• SQL Server Standard - basic features for small to medium businesses

• SQL Server Enterprise - advanced features for large businesses

• SQL Server Developer - full-featured version for development and testing

• SQL Server Web - designed for web applications

• SQL Server Business Intelligence - specialized for data analysis and reporting

Log shipping and performance tuning are important aspects of SQL Database Administration.

• Log shipping is a process of automating the backup of transaction log files on a primary database server and then restoring them onto a secondary server.

• Performance tuning involves identifying and resolving performance issues in a database system, such as slow queries or inefficient indexing.

• Techniques for performance tuning include query optimization, index tuning, and server configurati...read more

The best method for data migration from SQL to Azure depends on the specific requirements and constraints of the project.

• Consider the size and complexity of the database to determine the most suitable migration approach.

• Options include using Azure Database Migration Service, Azure Data Factory, or manual migration scripts.

• Evaluate factors such as downtime tolerance, data consistency, and cost when choosing the migration method.

• Test the migration process thoroughly before exec...read more

Truncate is faster and cannot be rolled back, while delete is slower and can be rolled back.

• Truncate is a DDL command, while delete is a DML command.

• Truncate removes all rows from a table, while delete removes specific rows based on a condition.

• Truncate resets identity column values, while delete does not.

• Truncate cannot be used with a WHERE clause, while delete can.

• Truncate is faster than delete as it does not log individual row deletions.

• Delete can be rolled back using a tr...read more

Database indexing is a way to improve query performance by creating a copy of a subset of data sorted in a specific order.

• Indexing is used to speed up data retrieval operations

• Types of indexing include clustered, non-clustered, unique, and full-text

• Clustered index determines the physical order of data in a table

• Non-clustered index creates a separate structure to store the index data

• Unique index ensures that each value in the indexed column is unique

• Full-text index is used to ...read more

Default fill factor is the percentage of space reserved for future data growth in an index.

• It is set to 0 by default, which means the index will be filled to 100% capacity.

• A fill factor of 80% means that 20% of the index space will be left empty for future growth.

• It can be set at the server, database, or index level.

• It can affect performance and disk space usage.

Design a comprehensive database for managing library operations, including books, members, and transactions.

• Create tables: Books, Members, Transactions, Authors, Categories.

• Books table: Fields - BookID, Title, AuthorID, CategoryID, ISBN, PublishedYear.

• Members table: Fields - MemberID, Name, Email, Phone, JoinDate.

• Transactions table: Fields - TransactionID, MemberID, BookID, IssueDate, ReturnDate.

• Authors table: Fields - AuthorID, Name, Bio.

• Categories table: Fields - CategoryID...read more

Integrating Transparent Data Encryption (TDE) with Always On Availability Groups requires specific steps for configuration.

• Ensure TDE is enabled on the primary database before adding it to an Always On group.

• Backup the TDE certificate and private key from the primary server.

• Restore the TDE certificate on all secondary replicas to ensure encryption compatibility.

• Use SQL Server Management Studio (SSMS) or T-SQL commands to configure the Always On Availability Group.

• Example T-SQ...read more