An index is performance tuning method of allowing faster retrieval of records from the table. An index creates an entry for each value and it will be faster to retrieve data. A view is a virtual table which consists of a subset of data contained in a table. Views are not virtually present, and it takes less space to store.
- The interviewer is likely asking this question to gauge the level of experience the SQL DBA has with backup and restore strategies.
- Database is nothing but an organized form of data for easy access, storing, retrieval and managing of data.
- Implementing security best practices involves using features like encryption, role-based access control, and auditing to protect data and resources.
- We need to pass database and file id details about that
specific database file for which we are looking for IO statistics. - The interviewer is also interested in understanding how the DBA would plan and implement an AlwaysOn Availability Group solution.
ACID stands for Atomicity, Consistency, Isolation, and Durability. It’s a set of properties that guarantee database transactions are processed reliably. A Non-Clustered Index does not alter the physical order of the data but creates a logical ordering of the data rows.
What are some of the best practices for SQL DBAs?
This may or may not negate all performance gains you might have achieved by calling update statistics. In fact, it could have a negative impact on performance depending on the characteristics of the system. Update Statistics is used to force a recalculation of query optimization statistics for a table or indexed view.
They must also be able to effectively communicate with other staff members, as they will often be working with teams of people in order to maintain the system. The interviewer is trying to gauge the interviewee’s experience with managing security for SQL Server databases. It is important to know this because it will help the interviewer determine if the interviewee is qualified for the position. The interviewer is asking this question to gain insights into the DBA’s past experiences and to see how they would approach resolving a disaster scenario. It is important for the interviewer to understand the DBA’s level of experience and knowledge so that they can gauge whether or not the DBA is a good fit for the company.
What is the difference between dropping a database and taking a database offline?
Because no one can memorize all the T-SQL syntax, a local copy of Books Online
is recommended to be available for candidates, but not access to the internet. For example, I am happy to hear a candidate tell me that if a table
is replicated, you cannot truncate it, it would be even better if the candidate
can give a reason. We will design a test case here by first creating a Salary table. To prevent phantom reads, we should set the isolation level in W3 to SERIALIZABLE. This will not work as the Dynamic Data Masking feature does not apply to the columns that are encrypted with the Always Encrypted feature.
An OUTER JOIN (LEFT, RIGHT, or FULL) returns all rows from one table and the matched rows from the other. A Data Type defines the type of data that can be stored in a table column, such as integer, character, date, etc. UNION combines the results of two or more SELECT statements and removes duplicate rows. UNION ALL also combines the results, but it includes all duplicates. The GROUP BY clause groups rows that have the same values in specified columns into summary rows, like « find the number of customers in each country. » Denormalization is the process of combining tables to improve query performance, at the expense of data redundancy.
Q82. Write a SQL query to get the third-highest salary of an employee from employee_table?
The calculated column is now part of the table and can be used in reports and visualizations. The Power BI REST API is a web service that enables developers to programmatically interact with Power BI components, such as datasets, reports, and dashboards. It allows for automation of tasks, integration with external applications, and customization of Power BI functionality. Developers can leverage the API to embed Power BI content, manage datasets, and perform various actions, enhancing the flexibility and extensibility of Power BI solutions. The “Star Schema” is crucial for its simplicity and efficiency in Power BI data modeling. It features a central fact table connected to dimension tables, forming a star-like structure.
They may describe a project they have worked on using Microsoft SQL Server or a complex challenge they have solved using this relational database management system. Skilled applicants will know that technical experts introduced transparent data encryption in 2008 to protect the files of the SQL Server database and prevent unauthorized access. SQL Server database administrators must work alongside other team members (such as users and developers) and communicate with them frequently. As after full backup LSN chain will break and if your full backups are corrupted than you can only go till first fullbackup and following transactional log backups.
What are the recovery models for a database?
Then, interview your best applicants to see who truly has the right skills and attitude to succeed at the role. Interviewing and hiring database administrators is tough for managers. It’s hard to understand what a DBA does, let alone whether or not the DBA is good at it. This is especially difficult in shops with just one DBA, and that DBA is now gone – or when you’re hiring your first DBA. Register for our free webinar to get insightful guidance from industry experts on how to crack technical interviews at the biggest companies in the world. Most top companies, including FAANG+ companies, prefer administrators with proven database and server-side experience.
Introduced in SQL Server 2008 Transparent Data Encryption (TDE) is a mechanism through which you can protect the SQL Server Database files from unauthorized access through encryption. how to become a sql dba developer Also, TDE can protect the database backups of the instance on which TDE was set up. Depending on the recovery model of a database, the behavior of the database log file changes.
