The Best 20 SQL Interview Questions Freshers and Experienced (2025)
SQL is still among the highly demanded skills in the data management and analytics field, as well as software and testing. It does not matter whether you are a fresher having your first interview or an experienced professional refreshing your technical interview, in 2025, it is a must that you have to be good with SQL.
Here in this blog, we have prepared the top 20 SQL interview questions which are generally and asked by MNC, startups and Tech giants along with simple, intermediate and advanced level queries.
Freshers Basic SQL Interview Questions
1. So what is SQL?
SQL is an acronym for Structured Query Language. It helps in the control and manipulation of relational databases by using commands such as SELECT, INSERT, UPDATE, and DELETE.
2. What are the various forms of SQL statements?
3. WHERE and HAVING clauses What is the difference?
The WHERE is to filter the rows prior to grouping.
HAVING is applied to exclude subsets of groups of aggregates (applied to GROUP BY ).
4. What are we talking about when we talk about a primary key?
Primary key A column or collection of columns which identifies every row of a table uniquely. It can neither include NULL value nor duplicates.
5. What is the INNER JOIN and LEFT JOIN difference?
INNER JOIN selects a row that has equal entries in both the tables.
LEFT JOIN is used to retrieve all the records in the left table plus the corresponding records found in the right table (or NULLs, otherwise).
Mid level SQL Interview Questions
6. Just what are indexes? What is the purpose of using them?
Indexes enhance quicker retrieval of information. They are made on columns usually IN WHERE conditions OR JOIN conditions.
7. What is normalization? State its types.
One method of arranging database tables so that there is less redundancy and enhanced data integrity is called normalisation.
A subquery is a dinning query within another query. It is employed to retrieve workplace results that are after that used by the principal query.
9. What is the meaning of UNION and UNION ALL?
UNION eliminates repetitions.
UNION ALL comprises all rows, even the duplicates.
10. What are the ACID features of a transaction?
Intermediate SQL Interview Questions (Mid-Level Questions)
11. What is CTE (Common Table Expression)?
A CTE is a working result group that may be cited inside a SELECT, INSERT, UPDATE or DELETE assertion. Stated with the WITH statement.
12. What are SQL window functions?
Window functions do their calculations on related rows to the current row, without summing them up and reducing the result set, E.g., RANK(), ROW_NUMBER(), LEAD(), and LAG().
13. When to use DELETE, TRUNCATE, and DROP?
14. State what is meant by the EXISTS vs. IN clause.
EXISTS looks at whether any rows exist and generally is more efficient when used with subqueries.
The IN looks at a value and compares it with values.
15. What are some of the ways to optimize a slow SQL query?
Use indexes
Avoid SELECT *
Employ JOINs effectively
Reduce with subqueries
Compare plan execution plans
16. What is stored procedure?
Stored procedure is a pre-compiled set of SQL statements that do a task. It is capable of accepting parameter and providing result.
A trigger is a procedural command that is automatically activated due to some events on a table (e.g., INSERT, UPDATE, DELETE and so forth).
18. How does a clustered index compare with a non-clustered index?
Clustered Index: Modifies the physical order of the data.
Non-clustered Index: has distinct structure to data row.
19. What is the solution to finding the 2nd highest pay in a table?
sql
Copy
Edit
SELECT MAX(salary)
FROM employees
WHERE salary less than (SELECT MAX(salary) FROM employees);
20. How do I write SQL queries using best practices in 2025?
Assign descriptive reserved words
Ensure queries are readable and well indented.
Those large sets should always be filtered
Track the performance with EXPLAIN plans
Elaborate on mediocre subqueries
Final Thoughts
SQL is among the leading skills of the data analysts, developers, testers, and business analysts in 2025. Regardless whether you are going to be interviewed in MNCs or startups, these are the top 20 must-know SQL interview questions that will make you feel more confident and prepared.
To become SQL adept or take your experience to the next stage, you may attend an SQL training in Hyderabad or look through online organisations with SQL certification courses suitable both to freshers and to the professionals with experience.
