Database Knowledge Point Notes

Source: Internet
Author: User

1. Dirty reads: One transaction is read to another transaction uncommitted update data.
Dirty reading means that when a transaction is accessing the data and the data has been modified, and the modification has not yet been committed to the database, another transaction accesses the data and then uses the updated data.

2. Phantom read: One transaction reads the newly inserted data that has been committed by another transaction.
For example, the first transaction modifies the data in a table, which involves all rows of data in the table. At the same time, the second transaction inserts a new row of data into the table. Then the first transaction finds that there are no modified rows of data in the table, as if the illusion had occurred.

3. Non-repeatable reads: One transaction reads the updated data that has been committed by another transaction.
Refers to a transaction two times for the same row of data query, because the second transaction during this time to modify this row data causes the first transaction two reads to the same row of data is called non-repeatable read

Database Knowledge Point Notes

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