Select Case SQL

How can I use conditional logic within a SELECT statement?

The SELECT CASE statement allows you to perform conditional logic within a SQL query, returning different values based on the evaluation of a given expression. It's a powerful tool for creating dynamic and flexible queries.

Thank you! Your submission has been received!

Oops! Something went wrong while submitting the form.

Description

The `CASE` statement in SQL is a powerful conditional expression that allows you to return different values based on the evaluation of a given condition. It's similar to an `if-then-else` statement in programming languages, but tailored for SQL queries. This flexibility is crucial for creating dynamic reports and data transformations. The `CASE` statement can be used in both `SELECT` and `UPDATE` statements. In `SELECT`, it allows you to derive new columns based on existing data. In `UPDATE`, it lets you modify data based on conditions. A key benefit of `CASE` is its ability to handle multiple conditions, making it suitable for complex decision-making within queries. It's a fundamental tool for data manipulation and analysis, enabling you to tailor your results to specific needs.

Why Select Case SQL is important

The `CASE` statement is essential for creating dynamic queries that adapt to different conditions. It allows for more complex data transformations and analysis, making it a valuable tool for data manipulation and reporting.

Example Usage


-- Find customers who live in 'New York' and have placed orders over $100
SELECT customerName, city, orderTotal
FROM Customers
WHERE city = 'New York' AND orderTotal > 100;

-- Find customers who live in 'New York' or 'Los Angeles'
SELECT customerName, city
FROM Customers
WHERE city = 'New York' OR city = 'Los Angeles';

-- Find customers who do not live in 'Chicago'
SELECT customerName, city
FROM Customers
WHERE NOT city = 'Chicago';

-- Find customers who live in 'New York' and have placed orders over $100 or have a specific product in their order history
SELECT customerName, city, orderTotal
FROM Customers
WHERE city = 'New York' AND (orderTotal > 100 OR productID = 123);

Common Mistakes

Forgetting the `END` keyword at the end of the `CASE` statement.
Using incorrect comparison operators (e.g., using `=` instead of `<>` or `!=`).
Not handling all possible cases within the `CASE` statement (resulting in unexpected default behavior).
Using incorrect data types in the `CASE` expression.

Select Case SQL

How can I use conditional logic within a SELECT statement?

Description

Why Select Case SQL is important

Example Usage

Common Mistakes

Want to learn about other SQL terms?

With Cte In SQL

Where Vs Having SQL

Windows Functions In SQL