mysql: How to update many to many relation table -

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I am using the cakepap for website development, now I have this table 

 < Code> id | Student_id Now my question is how to update this table, I am currently removing all previous figures of a particular student and linking new studentizations given by the student.   
 
 
 Based on what you are trying to do, it seems like a reasonable way to do so If you do not want to delete the previous special data, consider adding a timestamp and only one of the most recent questions in your question

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