mysql_commit() COMMIT ROLLBACK 提交 回滚 连接释放

MySQL :: MySQL 8.0 Reference Manual :: 28.7.7.6 mysql_commit() https://dev.mysql.com/doc/refman/8.0/en/mysql-commit.html

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28.7.7.6 mysql_commit()

bool mysql_commit(MYSQL *mysql)

Description

Commits the current transaction.

The action of this function is subject to the value of the completion_type system variable. In particular, if the value of completion_type isRELEASE (or 2), the server performs a release after terminating a transaction and closes the client connection. Call mysql_close() from the client program to close the connection from the client side.

Return Values

Zero for success. Nonzero if an error occurred.

Errors

None.

MySQL :: MySQL 8.0 Reference Manual :: 5.1.8 Server System Variables https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_completion_type

completion_type

Property	Value
Command-Line Format	--completion-type=#
System Variable	completion_type
Scope	Global, Session
Dynamic	Yes
SET_VAR Hint Applies	No
Type	Enumeration
Default Value	NO_CHAIN
Valid Values	NO_CHAIN CHAIN RELEASE 0 1 2

The transaction completion type. This variable can take the values shown in the following table. The variable can be assigned using either the name values or corresponding integer values.

Value	Description
NO_CHAIN (or 0)	COMMIT and ROLLBACK are unaffected. This is the default value.
CHAIN (or 1)	COMMIT and ROLLBACK are equivalent to COMMIT AND CHAIN and ROLLBACK AND CHAIN, respectively. (A new transaction starts immediately with the same isolation level as the just-terminated transaction.)
RELEASE (or 2)	COMMIT and ROLLBACK are equivalent to COMMIT RELEASE and ROLLBACK RELEASE, respectively. (The server disconnects after terminating the transaction.)

completion_type affects transactions that begin with START TRANSACTION or BEGIN and end with COMMIT or ROLLBACK. It does not apply to implicit commits resulting from execution of the statements listed in Section 13.3.3, “Statements That Cause an Implicit Commit”. It also does not apply for XA COMMIT, XA ROLLBACK, or when autocommit=1.

理解commit 

13.3.1 START TRANSACTION, COMMIT, and ROLLBACK Syntax

START TRANSACTION
    [transaction_characteristic [, transaction_characteristic] ...]

transaction_characteristic: {
    WITH CONSISTENT SNAPSHOT
  | READ WRITE
  | READ ONLY
}

BEGIN [WORK]
COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
ROLLBACK [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
SET autocommit = {0 | 1}

These statements provide control over use of transactions:

• START TRANSACTION or BEGIN start a new transaction.

• COMMIT commits the current transaction, making its changes permanent.

• ROLLBACK rolls back the current transaction, canceling its changes.

• SET autocommit disables or enables the default autocommit mode for the current session.

MySQL :: MySQL 8.0 Reference Manual :: 13.3.1 START TRANSACTION, COMMIT, and ROLLBACK Syntax https://dev.mysql.com/doc/refman/8.0/en/commit.html  

【如果在select读的情况下，假如认为对数据库无影响无烙印的操作，那么commit提交，就没有必要】

【连接的关闭：分为客户端、mysql服务端，都可以发起关闭】