Questions about MySQL querying multiple data

MySQL query for multiple data issues
Select multiple data how to find out what is repeated in the inside and indicate the last few days to insert the non-duplicate into the database

------Solution--------------------
If you want to clear the duplicate records inside the table, you can use INSERT into ..... SELECT ..... Statement is complete.
Create a table with the same structure as the original table, and insert all the records from the original table into the newly created table using the above statement. Create a new table, you need to create a unique composite index, so that when inserted, the same record will be automatically skipped without inserting.
The SQL statement for a unique composite index is similar to the following:

SQL Code

ALTER TABLE  ' mytable ' ADD UNIQUE (' username ', ' age ');
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