The database MySQL shows NULL even though the PUT data has been modified successfully, can you explain this?

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There can be several reasons for this. One possible reason is that the column in the database table where the data was updated is set to allow NULL values, and the system is not automatically updating it with the new values. Another possible reason is that there could be an error in the update query, causing it to not update the data as expected. Additionally, it is also possible that there is a problem with the way the query is being executed or the connection to the database. Without more information, it is difficult to determine the exact cause of the issue. It is recommended to check the database configuration and query syntax, as well as any error logs, to understand the reason for the issue.