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Using CASE WHEN in MySQL: Returning Different Values Based on Conditions

Using CASE WHEN in MySQL: Returning Different Values Based on Conditions

Introduction

MySQL, being one of the most popular relational database management systems, is widely used across various industries. During database querying, there are instances where it’s necessary to return different values based on specific conditions. In such cases, MySQL’s CASE WHEN structure comes in handy. This article explores how to use CASE WHEN in MySQL to return different values based on conditions.

What is the CASE WHEN Structure?

The CASE WHEN structure in MySQL is used to return different values based on specific conditions. This structure is typically employed within SELECT queries or UPDATE operations. Similar to an if-else statement, the CASE WHEN structure evaluates whether one or more conditions are met and returns the corresponding results.

Using CASE WHEN

Utilizing the CASE WHEN structure to return different values based on conditions is straightforward. Here’s the basic syntax:

SELECT 
    CASE 
        WHEN condition1 THEN result1
        WHEN condition2 THEN result2
        ...
        ELSE default_result
    END 
    AS column_alias
FROM 
    your_table;

In the above syntax:

  • Conditions such as “condition1” and “condition2” are evaluated.
  • The result corresponding to the first satisfied condition, such as “result1” or “result2”, is returned.
  • If none of the conditions are met, the default value specified as “default_result” is returned.


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Title: Using CASE WHEN in MySQL: Returning Different Values Based on Conditions


Introduction

MySQL, being one of the most popular relational database management systems, is widely used across various industries. During database querying, there are instances where it’s necessary to return different values based on specific conditions. In such cases, MySQL’s CASE WHEN structure comes in handy. This article explores how to use CASE WHEN in MySQL to return different values based on conditions.


What is the CASE WHEN Structure?

The CASE WHEN structure in MySQL is used to return different values based on specific conditions. This structure is typically employed within SELECT queries or UPDATE operations. Similar to an if-else statement, the CASE WHEN structure evaluates whether one or more conditions are met and returns the corresponding results.


Using CASE WHEN

Utilizing the CASE WHEN structure to return different values based on conditions is straightforward. Here’s the basic syntax:

sqlCopy code

SELECT CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ... ELSE default_result END AS column_alias FROM your_table;

In the above syntax:

  • Conditions such as “condition1” and “condition2” are evaluated.
  • The result corresponding to the first satisfied condition, such as “result1” or “result2”, is returned.
  • If none of the conditions are met, the default value specified as “default_result” is returned.

Examples

Let’s consider a few examples to illustrate the usage of CASE WHEN:

  • Evaluating a student’s performance based on their grade:
SELECT 
    student_name,
    CASE 
        WHEN grade >= 90 THEN 'AA'
        WHEN grade >= 80 THEN 'BA'
        WHEN grade >= 70 THEN 'BB'
        WHEN grade >= 60 THEN 'CB'
        WHEN grade >= 50 THEN 'CC'
        ELSE 'FF'
    END 
    AS performance
FROM 
    students;

In this query, a student’s performance is evaluated based on their grade, and the corresponding letter grade is returned.

  • Applying discounts based on a customer’s total purchase amount:
SELECT 
    customer_name,
    total_amount,
    CASE 
        WHEN total_amount >= 1000 THEN total_amount * 0.1
        WHEN total_amount >= 500 THEN total_amount * 0.05
        ELSE total_amount
    END 
    AS discounted_amount
FROM 
    orders;

This query calculates discounts based on a customer’s total purchase amount and returns the discounted amount accordingly.

Conclusion

In this article, we’ve learned how to use the CASE WHEN structure in MySQL to return different values based on conditions. The CASE WHEN structure enhances the flexibility of your database queries, allowing you to achieve various results based on different conditions. By leveraging this structure, you can exercise greater control over your database operations and obtain the desired outcomes.

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