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Transaction is actually a combination of database addition and deletion operations, it can be understood this way, when you type 1000 yuan to someone, there will be two changes in the database, one is that your money has decreased, the other is that that person's money has increased, and these two operations must be satisfied at the same time, otherwise the problem will be big, how to ensure that the two operations are all implemented, which requires the support of mysql transactions.

Mysql supports transactions, but first confirm that you are the InnoDB storage engine

Mysql transactions are designed to maintain the integrity of the database. Statements that are stacked in batches are either executed or not executed at all. Commonly used to manage insert delete and update statements.

Characteristics of the transaction:

1. Atomicity of transactions: a set of transactions that either succeed or are withdrawn.

2. Stability: illegal data (foreign key constraints, etc.) and transaction withdrawal.

3. Isolation: transactions run independently. If the result of one transaction affects other transactions, the other transactions will be withdrawn. 100% isolation of transactions requires the sacrifice of speed.

4. Reliability: after the software and hardware crash, the InnoDB data table driver will use log files to reconstruct and modify. You can't have both reliability and high speed, and the innodb_flush_log_at_trx_commit option determines when to save the transaction to the log.

Here are some commands that operate in mysql

The command set autoaction=0;// is used to cancel the autocommit of mysql. The begin;// transaction begins. Savepoint pointname;// sets up storage points and sets up multiple storage points that can be returned to one using rollback. Rollback pointname;// returns to a point. Rollback;// returns to begin if it does not use point. Commit;// can be submitted using commit if it can be submitted.

Use show variables like 'autocommit'; to view the status of the current autoaction

Here are the tests I performed under mysql:

You can see that using rollback goes back to the data before it was added.

Using the savepoint approach, readers can go down and test it.

The following is a test of transactions in C: (using the connect c package)

It looks like this when you first test the data in the previous table

My test code is as follows:

The my_sql.h here only gives the code for the transaction (the code for all operations of the database will be given in a later blog on manually setting up the http server). My_sql.h 13} 14 bool HttpSql::mysql_start () 15 {16 if (mysql_query (mysql, "SET autocommit=0") = = 0) 17 {18 cout

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