Top 10 SQL Queries Every Developer Must Know in 2025
Structured Query Language commonly knowns as SQL is the backbone of data management and has become the essential skill to learn in 2025. Whether you are making career in web development, data science, backend engineering expert in SQL is very much essential. Hiring managers not only look out for the query writing skill but also check your logical thinking, data manipulation skills and optimization knowledge.
If you are a beginner or preparing for interview these 10 SQL queries mentioned in this blog article will help you to master in 2025.
Basic SELECT Query
JOIN Queries
Aggregate Functions (COUNT, SUM, AVG, MIN, MAX)
GROUP BY with HAVING Clause
Subqueries (Nested Queries)
INSERT Statement
UPDATE Statement
DELETE Statement
DISTINCT Keyword
ALTER Table
SELECT are the foundation of SQL Query. You can expect a SELECT statement question in the interview. You should be able to fetch, filter, or show data from one or more tables in a readable format.
Example:
SELECT first_name, last_name, age FROM employees WHERE department = 'frontend';Explanation:
This Query will fetch first_name, last_name, age from employees, only from employees whose department is frontend.
Join operation is used to combines multiple tables. You should be able to work with INNER JOIN, LEFT JOIN, RIGHT JOIN and FULL JOIN.
Example:
SELECT orders.order_id, customer.name
FROM orders
INNER JOIN customers
ON orders.customer_id = customers.customer_id;
Explanation:
This Query will fetch order_id from orders table and name from customers table when customer_id from both the tables are matched. Knowledge of join operations is required to efficiently handle normalized databases.
Aggregate functions help you perform calculations on data, such as counting, summing, finding averages, etc. This is very useful in business analysis.
Example:
SELECT department, COUNT(*) AS num_employees
FROM employees
GROUP BY department;
Explanation:
This Query will count the employees from each department. Using aggregate functions with group by is important to summarize the data.
GROUP BY helps you summarize the data by grouping it, and the HAVING clause lets you filter the ungrouped results, which you cannot do with WHERE.
Example:
SELECT department, AVG(salary)
FROM employees
GROUP BY department
HAVING AVG(salary) > 50000;
Explanation:
In this query we calculate the average salary from every department but we will include only those departments where average salary is greater then 50,000
Subqueries means a query that is contained within another query, allow you to filter the results of one query for another query.
Example:
SELECT name
FROM employees
WHERE department_id = (SELECT department_id FROM departments WHERE department_name = 'IT');
Explanation:
In this query, the subquery fetches department_id from the departments table, and the outer query filters the employees based on the same department_id.
Adding new records in the database is done through INSERT statement. This is used for data population.
Example:
INSERT INTO employees (first_name, last_name, department_id, salary)
VALUES ('John','Doe',3,60000);
Explanation:
This query will insert a new record in the employees table. You must ensure that the data types given in the VALUES clause match the schema of the table.
UPDATE statement is used for modifying the existing records in the database. This is commonly used when you want to update any specific record.
Example:
UPDATE employees
SET salary = 40000
WHERE employee_id = 101;
Explanation:
This query will update the salary of the employee whose employee_id is 101. It is very important to use the WHERE clause correctly so that wrong records are not updated.
DELETE statement permanently remove records from the table. You should be careful as it permanently delets the data.
Example:
DELETE FROM employees WHERE employee_id = 101;
Explanation:
This query will delete the employee record from the EMPLOYEES table whose employee_id is 101.
DISTINCT keywords is used to remove duplicate records. If you want unique records then this query is useful.
Example:
SELECT DISTINCT department FROM employees;
Explanation:
This query will fetch distinct departments from the Employees table without duplicate department names.
ALTER TABLE statement is used to modify the table structure such as adding new columns or dropping a column.
Example:
ALTER TABLE employees ADD COLUMN date_of_birth DATE;
This query will add a column named date_of_birth to the Employees table. This query is required to modify the table.
Conclusion
SQL, despite being an old technology, is still highly relevant in 2025. These queries will help you effectively showcase your data manipulation and database management skills in the interview.
If you understand these queries well and practice them, you can perform confidently in your SQL interview. Also, basic knowledge of SQL is required in every tech job, so it is very important to include these queries in your skillset.
Good luck with your interviews and happy coding!
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