In SQL, we don’t always need all data. We need filtered data. For that, we use the WHERE Clause.
WHERE clause is like the Filter in Excel.
Syntax
SELECT column1, column2
FROM table_name
WHERE condition;
Let’s take a sample table Employees for all examples:
| ID | Name | City | Salary | Dept |
| 1 | Rakesh | Noida | 75000 | IT |
| 2 | Amit | Delhi | 45000 | HR |
| 3 | Priya | Noida | 80000 | IT |
1. WHERE with = (Equal to)
— Get all employees from Noida
SELECT * FROM Employees WHERE City = ‘Noida’;
2. WHERE with > , < , <> (Comparison)
— Salary greater than 50000
SELECT * FROM Employees WHERE Salary > 50000;
— Not from Delhi
SELECT * FROM Employees WHERE City <> ‘Delhi‘;
3. WHERE with AND, OR
— City is Noida AND Salary > 70000
SELECT * FROM Employees WHERE City = ‘Noida’ AND Salary > 70000;
— City is Delhi OR Noida
SELECT * FROM Employees WHERE City = ‘Delhi’ OR City = ‘Noida’;
4. WHERE with IN Operator
Instead of writing many OR, use IN. Very useful.
SELECT * FROM Employees WHERE City IN (‘Noida’, ‘Delhi’, ‘Gurgaon’);
5. WHERE with BETWEEN (Range)
— Salary between 40000 to 80000
SELECT * FROM Employees WHERE Salary BETWEEN 40000 AND 80000;
6. WHERE with LIKE (Search)
This is most important for Data Analysts.
— Name starts with R
SELECT * FROM Employees WHERE Name LIKE ‘R%’;
— City contains ‘oida’
SELECT * FROM Employees WHERE City LIKE ‘%oida%’
;
7. WHERE with NOT
— Employees NOT in HR
SELECT * FROM Employees WHERE Dept NOT IN (‘HR’);
Common Mistake in MS SQL Server
New users forget single quotes for text.
Wrong: WHERE City = Noida
Correct: WHERE City = ‘Noida’
Numbers don’t need quotes: WHERE Salary = 75000
Conclusion
WHERE Clause is 80% of SQL. If you master WHERE with AND, OR, IN, BETWEEN, LIKE – you can solve any interview query.
Practice Task: Write a query to get all IT department employees from Noida whose salary is more than 60000.
Answer in comments!