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This article mainly introduces "the types of MySQL locks and the basic principles of their use". In daily operation, I believe that many people have doubts about the types of MySQL locks and the basic principles of their use. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the doubts about the types and basic principles of MySQL locks. Next, please follow the editor to study!

At present, the main types of locks are as follows:

Read lock: when a transaction reads the corresponding dataset, a read lock is added. Read lock is also called Shared (S lock for short), because after a transaction adds a read lock to a dataset, it still allows other transactions to read the dataset.

Write lock: a write lock is added when a transaction writes to the corresponding dataset. Write locks are also called eXclusive (X locks for short) because after a transaction adds a write lock to a dataset, other transactions are no longer allowed to access the dataset.

Update lock: when a transaction updates the corresponding dataset, an update lock is added. Update locks are also known as U locks (abbreviations for Update). Generally speaking, this lock type is not required.

At present, many large database management systems add this lock type, mainly in order to improve the concurrency of system queries.

The basic principles of lock use are summarized as follows:

After an S lock is added to a dataset, it can be added to an S lock by other transactions, but no X lock or U lock can be added.

After an X lock is added to a dataset, it can no longer be added to any type of lock by other transactions

After adding a U lock to a dataset, considering the concurrency efficiency of the system, other transactions can be allowed to join the S lock, but absolutely not to add any X lock or U lock.

In the case of multiple copies, it is generally only necessary to add the S lock to any one copy, but to add the X lock requires the implementation of all replicas.

At this point, the study of "the types of MySQL locks and the basic principles for their use" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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