MySQL transaction

MySQL Business

Business profile

Business ： One or a group of sql Statements form an execution unit , Or all , Or none at all .
give an example ： Transfer accounts
user A Bank transfer is required , In this case, the transfer amount shall be deducted from the transfer out account , The amount transferred into the account needs to be added , These two operations are performed to ensure data consistency , Both success and failure are required , So you need to use transactions to process .

 Relating to affairs sql sentence 
commit : Commit transaction 
rollback : Roll back the transaction 

stay MySQL By default , Transactions are committed automatically , To perform a DML Statement opens the transaction , And automatically commit the transaction

The nature of transactions （ACID）

Atomicity （Atomicity）： Transaction is the smallest unit , Can not be further divided . Realize the atomicity of transactions , It's log based Redo/Undo Mechanism .
Uniformity （Consistent）： Transaction requires all DML Statement operation , Must guarantee both success and failure . The status before and after the transaction needs to be consistent , It can also be understood as data consistency .
Isolation, （Isolation）： Business A And transaction B Isolation between , You can set the isolation level of transactions .
persistence （Durable）： It's a guarantee of business , Flag for end of transaction ( Data in memory is persisted to hard disk file ). After a transaction is committed , The state of the transaction is persisted to the database , Update of data 、 Add and other operations will be persisted to the database .