A non-repeatable read occurs when during the course of a transaction, a row is retrieved twice and the values within the row differ between reads caused by a successfully committed change.
The key to non-repeatable reading is to modify:
In the same conditions, the data you have read, read it again, and find that the value is different.
The key point of the database phantom reads is to add or delete:
Under the same conditions, the number of records read out for the first time and the second time is different.