Advanced filtering and conditional expressions are powerful features in SQL that allow you to manipulate and filter data based on complex conditions. One commonly used tool for implementing conditional expressions is the CASE statement.

Advanced Filtering: Advanced filtering involves creating conditions that go beyond simple comparisons. It often includes logical operators (AND, OR, NOT) and comparisons involving multiple columns or subqueries. Advanced filtering allows you to retrieve specific subsets of data that meet intricate criteria.

SELECT name, age
FROM employees
WHERE department = 'Sales' AND (age > 30 OR experience_years > 5);

In this example, the query retrieves the names and ages of employees in the ‘Sales’ department who are either older than 30 or have more than 5 years of experience.

Conditional Expressions (CASE Statement): The CASE statement is a versatile way to introduce conditional logic into your SQL queries. It allows you to define conditions and specify corresponding values to be returned based on those conditions. The CASE statement is particularly useful when you need to transform data or assign custom labels based on certain conditions.

SELECT name,
age,
CASE
WHEN age < 18 THEN 'Minor' WHEN age >= 18 AND age < 60 THEN 'Adult'
ELSE 'Senior'
END AS age_group
FROM people;

In this example, the query calculates the age_group column based on the age column’s value. If the age is below 18, the person is labeled as a ‘Minor’. If the age is between 18 and 60, they are labeled as an ‘Adult’. Otherwise, they are labeled as a ‘Senior’.

The CASE statement is flexible and can be used in various scenarios, including aggregations, joins, and more. It helps simplify complex conditional operations within SQL queries and enhances the readability of your code.

Both advanced filtering and the CASE statement are valuable tools for querying and manipulating data based on intricate conditions, making your SQL queries more expressive and tailored to your specific needs.

Todo project CASE query:-

SELECT
users.name,
CASE
WHEN users.id > 40 THEN "greater than 40"
WHEN users.id < 40 THEN "less than 40"
ELSE "don't know"
END AS id_groups
FROM
users;