SQL Basics Interview Questions

Understanding SELECT and WHERE Clauses

The SELECT statement is used to retrieve data from one or more tables. The WHERE clause filters records based on specified conditions.

• SELECT column1, column2 FROM table_name;
• SELECT * FROM employees WHERE department = 'Sales';

Types of SQL JOINs

JOINs combine rows from two or more tables based on related columns. Common types include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN.

• INNER JOIN returns matching rows from both tables.
• LEFT JOIN returns all rows from the left table and matched rows from the right.
• RIGHT JOIN returns all rows from the right table and matched rows from the left.
• FULL OUTER JOIN returns all rows when there is a match in one of the tables.

Retrieve all employees from the Sales department

This query selects all columns for employees whose department is 'Sales'.

Count the number of employees in each department

Using GROUP BY and COUNT aggregate function to summarize data.