What does the mysql transaction isolation level mean?

This article mainly introduces the meaning of mysql transaction isolation level, which has certain reference value and can be used for reference by friends who need it. I hope you will learn a lot after reading this article. Next, let the editor take you to learn about it.

There are four levels of database isolation, as follows:

1. Uncommitted reads (Read Uncommitted): dirty reads are allowed, that is, data modified by uncommitted transactions in other sessions may be read

2. Read Committed: only the data that has been submitted can be read. Most databases, such as Oracle, default to this level (do not repeat)

3. Repeated Read: repeatable. All queries within the same transaction are consistent at the beginning of the transaction, the default level of InnoDB. In the SQL standard, this isolation level eliminates unrepeatable reads, but there are phantom reads, but innoDB solves phantom reads

4. Serial read (Serializable): fully serialized read, each read needs to acquire a table-level shared lock, and reads and writes will block each other.

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