Everyone wants to land a job that pays well and is in high demand, no two ways about it. After all, who doesn’t want to make money and gain some fame in the market? One of the most profitable industries across the globe is the tech industry. Every second person is willing to dive into this pool of opportunities.
Do you know which are some of the most, highest-paying jobs across the globe, especially in the technology landscape? Data analysts to database developers, database administrators, SQL server developers, software developers, consultants, .net developers, Big data engineers, and data scientists, now tell me what is the most common aspect among all these? Well, each one of these demands SQL.
Understanding SQL
SQL mainly stands for Structured Query Language, a core programming language highly considered for managing as well as manipulating relational databases. Now, usually, a team of developers and database administrators tends to interact successfully with all these databases.
So here, what SQL is supposed to do is, it seamlessly performs a wide range of operations such as querying and retrieving data, inserting new data, updating, as well as modifying all the existing data on these databases, and a lot more.
No wonder this technology is highly recommended among a wide range of database management systems as a consistent and powerful means, especially to conduct proper interaction and manage well-structured data. Some of the well-known relational database management systems to look out for include: Oracle, Microsoft SQL Server, PostgreSQL, MySQL, and SQLite.
These are also foundational tools used in delivering effective custom software development services tailored to business needs.
Back in the year 1986, this tech was standardized by the American National Standards Institute (ANSI), and it did succeed in gaining International Standard designation from the International Organization for Standardization (ISO) and, above all, has been adopted as a standard by numerous governments and organizational bodies worldwide.
Are you gearing up for your upcoming SQL interview? It’s pretty evident that’s why you are here. Well, we won’t upset you, but offer you a go-to guide featuring top SQL-based questions as well as answers worth considering. It doesn’t matter whether you are a job hunter, or hiring manager, or a top recruiter around, the following post will definitely help you better prepare for what to expect from the interviewer or even an interviewee for that matter.
Some general questions that you can ask to ease the mood can be:
- Are you familiar with all the flavours of SQL?
- Can you rate your level of proficiency in SQL?
- How many years have you been working in the field?
Let’s begin the drill! Now here’s a small piece of advice: whenever you are asked technical questions, just make sure you try to give a precise and crisp, and on-point response. Long answers could feel like you are beating around the bush or deviating from the main topic. And it also seems you are less confident.
Questions For Beginners
1. What is SQL?
SQL is mainly known for the structured query language, and the programming language is highly taken into consideration for interacting seamlessly with different relational database management systems, featuring fetching, updating, inserting, and removing data from tables.
2. Can you name some SQL dialects?
Well, there are numerous versions of SQL, some of which might be paid and some of which might be available for free. Some of the commonly used yet crucial ones include – Microsoft SQL Server, PostgreSQL, MySQL, SQLite, T-SQL, Oracle, and MongoDB.
3. Where is SQL mainly applied?
There are several possibilities using SQL, such as:
- Creating, deleting, and updating tables in a database
- Accessing, manipulating, and modifying data in a table
- Retrieving as well as summarising all the relevant information, be it from one table to several tables.
- Adding as well as removing certain rows and columns from the table.
4. Name different types of SQL commands
- Data Definition Language
- Data Manipulation Language
- Data Control Language
- Transaction Control Language
- Data Query Language
5. Define Join and its types
Join is a clause used to combine as well as retrieve different records from two or numerous tables. Of course, there are a few SQL tables that can be joined seamlessly on the basis of the relation between different columns. The top types of Join include:
- (Inner) Join – This type of join returns mainly those records that satisfy a well-defined join condition for multiple tables, this one is the default SQL join.
- Left (Outer) Join – This type returns all records from the left table, and the remaining right table satisfies a well-defined condition.
- Right (Outer) Join – Here, all records from the right table are returned, and from the left table showcase a defined join condition.
- Full (Outer) Join – All the records from both tables are returned, so this is usually a rare combination of left and right joins.
Questions For Intermediate
1. Define the meaning of function in SQL Why is it being used?
This is basically a database object successfully representing a proper set of SQL statements that are used again and again to conduct a certain kind of task. Here, different kinds of parameters are incorporated and different calculations are performed, or other relevant manipulations are performed. On and all, functions can assist in enhancing code readability and, of course, avoid repetition of the same code snippets. Common types of functions include:
- Aggregate functions
- Scalar functions
2. Can you give some examples of character manipulation functions?
Character manipulation functions mainly represent a subset of character functions and the way they are used to modify the text data.
- CONCAT() – Joins two or more string values; here it assists in appending the second string to the end of the first one.
- SUBSTR() – This type mainly returns a part of a string satisfying different start and end points.
- LENGTH() – This character function returns the length of a string featuring different blank spaces.
- REPLACE() – All the occurrences of a defined substring in a provided string with another substring.
- INSTR() – All the numeric positions of a defined substring in a pre-defined string.
- LPAD() and RAPD() – Return the padding of the left-side/right-side character for right-justified/left-justified value
- TRIM() – All the defined characters can be removed here; this also includes different white spaces as well, from the left, right, or even both ends of a provided string.
3. Can you spot the difference between a stored procedure and a function?
A stored procedure is mainly a precompiled set of SQL statements that can be seamlessly executed as a single unit, and it is mainly used to perform a specific range of tasks. Now functions are unable to return multiple sets and modify database objects, whereas stored procedures can. Though functions can return a single value, and are unable to modify data.
4. How many set operators are you well aware of?
- UNION – All the records that are mainly obtained by one or two queries can be returned successfully, now this doesn’t include any duplicates.
- UNION All – All the records that are obtained by at least one or two queries can be returned, which does incorporate duplicates.
- Intersect – This returns the records that are obtained by both queries.
- Except – Also known as MINUS in MySQL and Oracle, this type successfully returns only the records that are successfully obtained by the first query, but unfortunately, doesn’t include the second one.
5. How many types of SQL relationships are you aware of?
- One-to-one – Each record in one table corresponds well to only one record in another table.
- One-to-many – Here, recording is successfully done in one table, which corresponds successfully to a wide range of records in another table.
- Many-to-many – Each record is represented in both tables, which successfully corresponds to different records in another table.
Questions for Advanced Level Candidates
1. What is a high-availability solution for a SQL server environment? Is there any other way to implement a disaster recovery plan to minimise downtime and data loss?
Well, yes, it is quite possible. All you need to do this is to use always-on availability groups used for high availability, setting up primary and secondary replicas among different servers, which is done among separate geographical locations. So, as per the duty of the primary replica, all transactions are handled, and for the secondary one, everything is kept in sync.
Now this was about a high availability solution, and when it comes to disaster recovery, it’s time to configure a secondary replica in a remote data center with automatic failover. So all this leads to minimal downtime and no data loss. In case the primary server fails, regular backups can be quite helpful here, and the failover procedures are tested to ensure reliability.
2. Tell me some of the best security practices that must be followed, especially when setting up and managing a SQL Server database
One of the best ways to ensure security is to follow the principle of least privilege, assigning only the minimal permissions required for each task. It is also advisable to integrate SQL Server with Active Directory for secure authentication and to use encryption for sensitive data with tools like Transparent Data Encryption (TDE). Additionally, regular patching and thorough security audits are essential for monitoring and preventing unauthorized access. Conducting regular penetration testing helps identify vulnerabilities before attackers can exploit them, making it a critical part of a strong security strategy. Keeping close tabs on the system allows for quick detection and response to any security issues.
Conclusion
So that’s all for now! The best way to ace the SQL interview is to keep on practising as much as you can. Try to solve more and more such questions, read relevant books, and be thorough with the knowledge, rather than sounding superficial.
I hope you did find the following post worth taking into account. In case you have any kind of doubts or queries, feel free to mention them in the comment section below. Good luck with the upcoming interview! Keep reading the post to get more information and updates regarding the same.
