Why is My MySQL Trigger Not Updating the Table?

Troubleshooting MySQL Trigger Inactivity

When creating a simple MySQL trigger that is expected to update a column based on changes in another column, it's essential to address potential issues that may hinder its functionality. One common challenge is the inability of a stored function or trigger to modify a table that is already in use.

Error Message: Table in Use by Invoking Statement

The error message "Can't update table pos_table in stored function/trigger because it's already used by statement which invoked this stored function/trigger" indicates that the table being updated by the trigger is also being used by the statement that triggered the operation. This conflict prevents the trigger from executing correctly.

Solutions:

To resolve this issue, consider using a BEFORE INSERT trigger instead of an AFTER UPDATE trigger. BEFORE INSERT triggers allow modifications to the values being inserted before they are stored in the table, eliminating the conflict with the invoking statement.

Additionally, using the NEW keyword in the trigger to update the value in a specific row ensures that only the modified row is updated, rather than the entire table as suggested by the provided UPDATE statement.

Simplification of PTS Calculation:

Finally, it's worth noting that storing the PTS values in a separate column may not be necessary. The PTS value can be easily calculated dynamically when needed, simplifying the code and avoiding the aforementioned trigger issue.

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