How to Write Case in Where Condition in SQL
Writing SQL queries can sometimes become complex, especially when you need to perform conditional logic within your queries. One common scenario is using the CASE statement in the WHERE condition. This allows you to filter records based on multiple conditions and perform actions accordingly. In this article, we will discuss how to write a CASE statement in the WHERE condition in SQL and provide some practical examples to help you understand the process.
Firstly, let’s understand the basic structure of a CASE statement in SQL. The CASE statement is used to perform conditional logic and return different values based on the evaluation of one or more conditions. The syntax for a CASE statement is as follows:
“`sql
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
…
ELSE default_result
END;
“`
Now, to incorporate the CASE statement in the WHERE condition, you need to use the CASE statement within the WHERE clause. This allows you to filter records based on the conditions specified in the CASE statement. Here’s an example to illustrate this:
“`sql
SELECT
FROM employees
WHERE CASE
WHEN department = ‘Sales’ THEN 1
WHEN department = ‘Marketing’ THEN 2
ELSE 0
END = 1;
“`
In this example, we are selecting all records from the `employees` table where the department is ‘Sales’. The CASE statement evaluates the department column, and if the value is ‘Sales’, it returns 1. The WHERE clause then filters the records based on this condition, and only the records with a department value of ‘Sales’ will be returned.
You can also use the CASE statement to filter records based on multiple conditions. Here’s an example:
“`sql
SELECT
FROM sales_data
WHERE CASE
WHEN sales_amount > 10000 THEN ‘High’
WHEN sales_amount > 5000 THEN ‘Medium’
ELSE ‘Low’
END = ‘High’;
“`
In this example, we are selecting all records from the `sales_data` table where the sales_amount is greater than 10,000. The CASE statement evaluates the sales_amount column, and if the value is greater than 10,000, it returns ‘High’. The WHERE clause filters the records based on this condition, and only the records with a sales_amount greater than 10,000 will be returned.
By using the CASE statement in the WHERE condition, you can perform complex conditional logic and filter records based on various criteria. This can be particularly useful when you need to perform actions based on specific conditions within your SQL queries. Remember to practice and experiment with different scenarios to become proficient in using the CASE statement in the WHERE condition in SQL.
