Transactions in the database

A transaction (Transaction) is the basic unit of concurrency control. The so-called transaction, which is a sequence of operations that are either executed or not executed, is an inseparable unit of work. For example, a bank transfer job: Debit from one account and add another account, both of which are either executed or not executed. Therefore, they should be regarded as a business. A transaction is a unit of data consistency maintained by a database that maintains data consistency at the end of each transaction.

A transaction has the following 4 basic characteristics.

Atomic (atomicity): The operations contained in a transaction are considered to be a logical unit in which the operations of the logical unit either succeed or fail altogether.

Consistency (consistency): only legitimate data can be written to the database, or the transaction should roll it back to its original state.

Isolation (Isolation): Transactions allow multiple users to concurrently access the same data without destroying the correctness and integrity of the data. At the same time, the modification of parallel transactions must be independent of the modifications of other parallel transactions.

Durability (persistent): After the transaction ends, the result of the transaction must be cured.

Statement of the transaction
Start things: Begin TRANSACTION mysql_query (' Start TRANSACTION ');//Start transaction
Commit a thing: Commit TRANSACTION mysql_query (' commit ');//Commit a transaction
ROLLBACK TRANSACTION: ROLLBACK TRANSACTION mysql_query (' ROLLBACK ');//ROLLBACK TRANSACTION

The display transaction is identified with BEGIN TRANSACTION and end transaction, where the update and DELETE statements are either all executed or not executed at all. Such as:
BEGIN TRANSACTION T1
Update student
Set Name= ' Tank '
where id=2006010
Delete from student
where id=2006011
Commit
Simply put, a transaction is a mechanism that maintains the integrity of the database.

The implementation form is to embed ordinary SQL statements into the BEGIN Tran ... Commit Tran (or full form Begin Transaction ... Commit Transaction), of course, you can also use rollback Tran to rollback a transaction, which is the undo operation, if necessary.

Transactions in the database