Every industry knows the importance of data and its underlying power. The data collected by business houses is analyzed and used for various decision-making activities. It is important to have a good SQL programmer in the team to gain maximum information from the given data. Let us know about that the SQL Query Interview Questions.
An SQL programmer needs to be knowledgeable and proficient in the language. He/she should know all the basic and practical concepts of programming. The aspirant is subjected to various programming skill tests to find a candidate with correct work experience. It is also important for business houses to find a suitable candidate with relatable work ethics. We have compiled various sets of questions that can be asked during interviews.
An aspirant can be evaluated at three levels
- Data operator (Basic) entry-level
- Mid-level (Moderate) programming level
- Senior level (Complex) programming level
Entry-level Evaluation
If an organization is searching for an entry-level SQL programmer, the aspirant is likely to have limited experience. You can ask concept-based questions to evaluate his/her fundamental knowledge of SQL.
- Can you differentiate data from information?
- How can you convert raw data into useful information?
- Explain the importance of data analysis in today’s life.
- Is there any distinction between instance and schema?
- How can you distinguish between a database and a database management system?
- Give at least three instances of Database Management systems.
- Are SQL and MySQL being same?
- Explain RDBMS and give an example of it.
- Who is a database administrator?
- Can you explain the duties of a database administrator?
- How can databases be classified?
- Why managing a database is important?
- Can you explain the transaction with the help of a diagram?
- What is the meaning of Views in DBMS?
The solution to the above questions can be seen in any database book or online platform. However, we are providing keys to few questions for your consideration.
Can you differentiate data from information?
A: Data is the raw form of facts and figures whereas information is the inclusion of context to data.
Is there any distinction between instance and schema?
A: Schema can be seen as the architecture of database whereas instance is its content.
Can you explain the duties of a database administrator?
A: All the maintenance, security concern and ensuring availability of data is within the job profile of database administrator.
Mid-Level Position Evaluation
An organization may need an SQL programmer with 3 -5 years of experience to ensure that data is properly stored, maintained, and analyzed. The experienced programmer will bring a practical approach to the data analysis.
The efficiency and knowledge of the programmer can be checked by various moderately complex questions such as:
· Consider the below two tables
Table – Employee_P_Details
| Emp_Id | Full_Name | Manager_Id | Date_Of_Joining | City |
| 111 | John | 314 | 01/31/2014 | New York |
| 121 | Sam | 389 | 01/30/2015 | San Francisco |
| 141 | Sandy | 387 | 27/11/2016 | California |
Table – EmployeeSalary
| EmpId | Project | Salary | Variable |
| 111 | P13 | 8000 | 5000 |
| 121 | P23 | 10000 | 10000 |
| 121 | P13 | 12000 | 20000 |
Can you write a query to find the names of all employees who have not joined the organization in 2020?
Can you find the details of all employees in relation Employee_P_Details that draw a salary of more than $.10, 000?
- How many employees are working on each project? Fetch the data project-wise if possible.
- Can you determine the name of the employee that draws the third-highest salary from the relations given above?
- Is it possible to find common records from two tables? If yes, write the query for that.
Various other questions related to the functioning of the database can be asked
- What do you mean by aliases? Why are they used in the database?
- What is the “select into” command? Can you write its syntax?
- Is it possible to show only even rows from a table?
- Explain the usage of “Default Constraint”.
- Why the relations in a database are maintained in their normal form?
- Can you explain denormalization with an example?
- Can you tell us something about transaction control processing?
- Explain the functioning of “Commit” and “Rollback” commands.
- Is there any difference between the unique key and the Primary key?
- Add a primary key to an existing table.
- Is SQL a case-sensitive language?
- Differentiate between SQL and Oracle?
Here, we are also providing keys to few questions for your consideration.
Is SQL a case-sensitive language?
A: SQL server is case insensitive. But a database administrator can make in case sensitive for extra security.
Differentiate between SQL and Oracle?
A: Both are the language used to access and manipulate database but have different capabilities.
Senior Level Evaluation
If an organization is searching for an SQL programmer, it is important to check his/her skills in data recovery and maintenance of data integrity. The aspirant should also be proficient in the working of a database administrator.
- Why triggers are used in the database?
- What should be the frequency of database backup for our organization?
- Is it advisable to use a cloud facility for data storage?
- How can we ensure data safety without hampering the availability of data on the server?
- Is it necessary to have a firewall on our server?
- What are views? Can you write its syntax?
- How does index hunting help in increasing the efficiency of a database?
- Can you name two clauses used in SQL? Write the syntax of both.
- What is the difference between clustered and non-clustered indexes?
Here, we are also providing keys to few questions for your consideration.
Why triggers are used in the database?
A: Trigger is considered as a collection of statements that can be used by many programs.
Is it necessary to have a firewall on our server?
A: Yes, it is. Firewall is an essential part of security system that need to maintained to protect from various cyber threats.
Conclusion
Data is a tool that can help us to devise a business strategy and analyze its outcome in a more effective way. However, it is important to hire an efficient database analyst and a database programmer to fetch the right information from the raw data. The above-mentioned questions will help an organization to hire the best suitable aspirant. Candidates who are interested in making a career in the database can also prepare these questions for their interviews.
Frequently Asked Questions
Q: I have a small retail store. How does using database software can help me to grow my business?
A: Database software can help any business to grow. It helps to manage, view and analyze data in a more effective way. You can hire a software programmer to develop software according to your needs. You can ask the programmer to make provision of sales analysis by product, month and brand. It will help you to understand the demand of various products and brands.