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SUM CASE WHEN in SQLite: Calculating Conditional Totals by user_id

Summary: Learn how to use the `SUM CASE WHEN` statement in SQLite to calculate conditional totals by `user_id` after creating a new column. Ideal for intermediate users looking to enhance their database querying skills. --- SUM CASE WHEN in SQLite: Calculating Conditional Totals by user_id If you're working with SQLite and need to calculate conditional totals based on specific criteria, you're likely to encounter the SUM CASE WHEN statement. This operation can be particularly useful when you're dealing with user-based aggregations or other conditional sums in your database. In this guide, we'll walk you through how to achieve this in SQLite, especially after creating a new column. Understanding the Scenario Imagine you've added a new column to your SQLite table and want to sum values based on certain conditions for each user. For instance, you may have a transactions table where you want to sum up the transaction amounts only for successful transactions for each user_id. Step-by-Step Walkthrough Let's assume you have a transactions table structured as follows: [[See Video to Reveal this Text or Code Snippet]] You want to sum the amount for transactions with a status of 'successful' for each user_id. Here’s how you can achieve this using SUM CASE WHEN: Insert Sample Data For demonstration purposes, we'll insert some sample data into the transactions table: [[See Video to Reveal this Text or Code Snippet]] Using SUM CASE WHEN To get the sum of amount for successful transactions grouped by user_id, you can use the following SQL query: [[See Video to Reveal this Text or Code Snippet]] This query works as follows: The CASE WHEN statement checks if the status is 'successful'. If it's true, it includes the amount in the sum. If it's false, it includes 0 instead. The SUM function then calculates the total of these conditional values. Finally, the results are grouped by user_id. Result Interpretation Running the above query will yield the following results: [[See Video to Reveal this Text or Code Snippet]] For user_id 1, the sum of successful transaction amounts is 100.0. For user_id 2, the sum is 275.0. For user_id 3, there are no successful transactions, so the sum is 0.0. Conclusion Using the SUM CASE WHEN statement in SQLite enables you to perform powerful conditional aggregations, perfect for tasks like summing transaction amounts based on user-specific criteria. This approach can be adapted to a wide range of conditions and use cases, offering flexibility and precision in your database queries. We hope this guide helps you better understand and utilize the SUM CASE WHEN statement in SQLite to meet your data aggregation needs.