How to Filter Data in MySQL Using the WHERE Clause

4. BETWEEN Operator

The BETWEEN operator is used to select data within a specific range of values, including upper and lower bound values. This is especially useful when we want to get data between two specific values.

SELECT prod_name, prod_price
FROM products
WHERE prod_price BETWEEN 5 AND 10;

This statement will take all products priced between 5 and 10, including the price of 5 and 10 itself.

5. IS NULL Operator

The IS NULL operator is used to check for columns that have no value or contain NULL values. The use of this operator is important for finding empty or unfilled data.

SELECT cust_name
FROM customers
WHERE cust_email IS NULL;

This statement will display all the names of customers who don’t have an email address listed.

A NULL value is different from a value of 0 or an empty string; NULL indicates no data or has not been filled in at all.

Conclusion

The WHERE clause in SQL serves to filter the data by specifying certain conditions that must be met. It allows users to retrieve a piece of data from a large table.

By using operators such as equal to (=), not equal to (<> and !=), as well as comparison operators (<, >, <=, >=), users can perform various tests against the value. The BETWEEN operator is used to filter data within a specific range of values, while the IS NULL operator is used to check if there is an empty (NULL) value in the column.

The proper use of WHERE clauses can improve query performance and ensure that only relevant data is retrieved, making it easier to analyze and make decisions. Best practices include using appropriate operators and avoiding filtering at the application level to maintain system efficiency.