How to resolve the issue of sum returning null in MySQL?

In MySQL, when the SUM function returns NULL, it is usually because there is no data in the corresponding column or because there are NULL values. Solutions include:

1. You can use the IFNULL function within the SUM function to replace NULL values with 0. For example:

SELECT SUM(IFNULL(column_name, 0)) FROM table_name;

1. You can use the COALESCE function with the SUM function to replace NULL values with 0. For example:

SELECT SUM(COALESCE(column_name, 0)) FROM table_name;

1. Check the data: Make sure there is data in the corresponding column. If there is no data or there are NULL values, you can resolve it by updating the data or inserting new data.

By using the above method, you can resolve the issue of the SUM function returning NULL in MySQL.