Linux下MySQL使用InnoDB引擎筆記

前言:把日常工作以及學習過程中遇到的問題,常記筆記總結我覺得是非常有必要的,不僅可以方便以後在類似過程中遇到同樣問題方便查找和解決,也便於其他需要幫助的人們可少找彎路!

一.簡介:
1.最近在Linux下使用MySQL數據庫時,爲了支持事務操作需要用到InnoDB引擎,對於表中處理的插入,更新等操作失敗時,回滾前面不應該完成的操作是必須的.

2.一般MySQL默認的數據庫引擎是MyISAM,不支持事務和外鍵,則可使用支持事務和外鍵的InnoDB引擎.關於如何在Linux下設置MySQL默認引擎InnoDB請參照我前面寫的一篇文章小結

http://blog.csdn.net/sunrier/article/details/7475403

3.本筆記着重講解MySQL的autocommit變量,如何在數據庫中設置自動提交,禁止自動提交,如何在對錶操作失敗後回滾,對錶操作成功後提交事務!

二.操作方法
MySQL的autocommit默認是打開的(ON爲打開,OFF爲關閉或者表示成1爲打開,0爲關閉)
打開或關閉即是打開自動提交或者關閉自動提交

1.MySQL命令:

mysql>

顯示結果爲ON,表示事務自動提交,即不用手工去commit。當然,你可以設置其爲OFF,然後自己手工去commit。

1.12)打開和關閉自動提交功能命令:
   關閉自動提交功能命令
   mysql> set session autocommit=OFF;

   mysql>
   或者
   mysql> set session autocommit=off;
   Query OK, 0 rows affected (0.00 sec)

   mysql>
   (注:off不區分大小寫)

   設置後再次查看:
   mysql> show variables like '%autocommit%';
   +---------------+-------+
   | Variable_name | Value |
   +---------------+-------+
   | autocommit    | OFF    |
   +---------------+-------+
   1 row in set (0.01 sec)

   mysql>

   可猜測mysql> set session autocommit=on;應該爲打開自動提交功能,不過猜是猜的,最好還是實踐下這個命令打開自動提交功能命令
   mysql> set session autocommit=ON;

   mysql>

mysql>

注:如果退出MySQL,下次登陸MySQL後autocommit還會自動設置爲默認的變量,這裏即autocommit爲ON,事務自動提交

方法2:
1.21)如果你在剛纔上面方法1.11)中查看參數出現下面的情況:
mysql> show variables like '%autocommit%';
Empty set (0.00 sec)

   mysql>
   這個情況在我裝的虛擬機上就無法查看,然後在公司的服務器上安裝的MySQL就沒問題(注1.1X爲公司的MySQL)。
   現在關於爲什麼會出現兩種不同的結果,筆者還沒解決這個問題,猜測可能是因爲數據庫版本的不同可能查看的命令不一樣,我最終在網上查找到例外的方法在命令下查看和設置autocommit變量

1.22)查看和設置autocommit變量

    查看autocommit變量
    mysql> select @@autocommit;
    +--------------+
    | @@autocommit |
    +--------------+
    |            1 |
    +--------------+
    1 row in set (0.00 sec)

mysql>
注:autocommit爲1表示打開自動提交

    設置autocommit變量
    mysql> set session autocommit=off;
    Query OK, 0 rows affected (0.00 sec)

    mysql> select @@autocommit;
    +--------------+
    | @@autocommit |
    +--------------+
    |            0 |
    +--------------+
    1 row in set (0.00 sec)

    mysql>
    注:autocommit爲0表示關閉自動提交

2.MySQL的配置文件my.cnf:
修改autocommit變量也可以通過修改配置文件my.cnf來關閉autocommit
[mysqld]
init_connect='SET autocommit=0' //在my.cnf文件[mysqld]下面加上這句

3.MySQL數據庫程序中使用C的API函數:

切換autocommit模式，ON/OFF:
my_bool mysql_autocommit(MYSQL *mysql, my_bool mode)
如果模式爲"1",啓用autocommit模式;如果模式爲"0",禁止autocommit模式.
返回值:如果成功返回0;如果出現錯誤返回非0值.

回滾當前事務:
my_bool mysql_rollback(MYSQL *mysql)
該函數的動作取決於completion_type系統變量的值.尤其是如果completion_type的值爲"2",終結事務後,服務器將執行釋放操作,並關閉客戶端連接.客戶端程序應調用mysql_close(),從客戶端一側關閉連接.
返回值:如果成功返回0;如果出現錯誤返回非0值.

提交當前事務:
my_bool mysql_commit(MYSQL *mysql)
該函數的動作受completion_type系統變量的值控制.尤其是如果completion_type的值爲2,終結事務並關閉客戶端連接後,服務器將執行釋放操作.客戶端程序應調用mysql_close(),從客戶端一側關閉連接.
返回值:如果成功返回0;如果出現錯誤返回非0值.

三.實例說明:
1.MySQL下命令實例(注:student爲我的MySQL數據庫test中先前已經創建的一個student表信息):

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   24 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
+--------+---------+------+
6 rows in set (0.00 sec)

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)

mysql>

從上面可以看出此時數據庫autocommit爲1也就是自動提交
下面我想插入一個學生信息學號,名字,年齡分別是7,Nicky,22

mysql> insert into student values (7,"Nicky",22);
Query OK, 1 row affected (0.00 sec)

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   24 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
+--------+---------+------+
7 rows in set (0.00 sec)

mysql>

從MySQL插入命令後,執行查詢結果可以看出,剛纔插入的一條學生記錄(7,"Nicky",22)已經插入到表裏面,也許你爲了保證執行結果確實是這樣,你可能先退出MySQL,再次進入MySQL再查詢下,出於這樣的本能,我也是這樣做的

mysql> exit
Bye
[root@localhost ~]# mysql -uroot -predhat test
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 11 to server version: 5.0.22

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   24 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
+--------+---------+------+
7 rows in set (0.00 sec)

mysql>

這樣可以確信剛纔那條學生記錄已經確實插入到數據庫test的student表裏了.

開始主要的環節:

mysql> set session autocommit=off;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 0 |
+--------------+
1 row in set (0.00 sec)

mysql>

從上面可以看出此時數據庫變量autocommit已經被設置爲0也就是禁止自動提交
下面我想插入一個學生信息學號,名字,年齡分別是8,Jerry,21

mysql> insert into student values (8,"Jerry",21);
Query OK, 1 row affected (0.00 sec)

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   24 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
|      8 | Jerry   |   21 |
+--------+---------+------+
8 rows in set (0.00 sec)

mysql>

從MySQL插入命令後,執行查詢結果可以看出,剛纔插入的那條學生記錄(8,"Jerry",21)也插入到表裏面了。
也許你還是爲了保證執行結果之外,你可能先退出MySQL,再次進入MySQL再查詢下

[root@localhost ~]# mysql -uroot -predhat test
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 12 to server version: 5.0.22

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   24 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
+--------+---------+------+
7 rows in set (0.00 sec)

mysql>

可以看出剛纔那條學生記錄(8,"Jerry",21)沒有真正插入數據庫test的student表裏,這應該就是沒有自動提交的效果,
說明了剛纔設置變量autocommit爲0時後來產生了作用。那麼現在你也許會想,我現在設置了變量autocommit爲0,不自動提交執行結果了,那我應該怎麼做才能使我執行的SQL語句還一樣對數據庫產生影響呢???基於這樣的思考和探索下,對於我來說,我剛開始也一無所知,好在現在網絡資源強大,我可以利用百度,google等可以利用的資源, 在網上找到了不少相關的知識介紹
發現了下面兩個SQL命令:
mysql> rollback;

mysql> commit;

從字面意思上我們可以猜出了它們的大概意思rollback即回滾,commit即提交.現在回到剛纔沒有插入成功的那條記錄那,爲了我能夠在數據庫中變量autocommit設置爲0的情況下,執行SQL命令也能對數據庫產生影響,那就需要在執行DML的SQL命令後,執行一個commit提交命令

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)

mysql> set session autocommit=off;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 0 |
+--------------+
1 row in set (0.00 sec)

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   24 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
+--------+---------+------+
7 rows in set (0.00 sec)

mysql>

上面爲重新設置和查看,可以發現autocommit設置爲0

mysql> insert into student values (8,"Jerry",21);
Query OK, 1 row affected (0.00 sec)

mysql> commit;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   24 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
|      8 | Jerry   |   21 |
+--------+---------+------+
8 rows in set (0.00 sec)

mysql> exit
Bye
[root@localhost ~]# mysql -uroot -predhat test
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 13 to server version: 5.0.22

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   24 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
|      8 | Jerry   |   21 |
+--------+---------+------+
8 rows in set (0.00 sec)

mysql>

這樣可以確信剛纔那條學生記錄(8,"Jerry",21)已經確實插入到數據庫test的student表裏了.

總結:在數據庫中autocommit設置爲0的情況下,所有的SQL執行命令的結果在遇到commit命令之後才真正提交到數據庫中。也許到這會你發現我剛纔說了兩個SQL命令,到現在只說了commit命令,還有個rollback命令怎麼用呢?

繼續rollback命令

現在我想把數據庫test的student表裏名字爲"Sunrier"這個小朋友的信息刪除了。

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)

mysql> set session autocommit=off;
Query OK, 0 rows affected (0.00 sec)

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
| 0 |
+--------------+
1 row in set (0.00 sec)

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   24 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
|      8 | Jerry   |   21 |
+--------+---------+------+
8 rows in set (0.00 sec)

mysql> delete from student where fname = "Sunrier";
Query OK, 1 row affected (0.01 sec)

mysql> select * from student;
+--------+--------+------+
| studno | fname | age |
+--------+--------+------+
|      1 | Jack   |   67 |
|      2 | Tim    |   22 |
|      4 | Helen |   26 |
|      5 | Tony   |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky |   22 |
|      8 | Jerry |   21 |
+--------+--------+------+
7 rows in set (0.00 sec)

mysql>

從表裏面可以看到名字爲"Sunrier"的信息刪除了,也許你可能馬上後悔自己的選擇,我找不到任何理由刪除"Sunrier",這個小朋友,馬上我着急了,我該如何找到該小朋友的原始信息呢,於是你眼前一亮,rollback這個命令,回滾,按照日常的用語是不是回過去的意思.於是你查詢了下相關資料,好像可以哎,於是決定自己試試這個SQL命令

mysql> rollback;
Query OK, 0 rows affected (0.00 sec)

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   23 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
|      8 | Jerry   |   21 |
+--------+---------+------+
8 rows in set (0.00 sec)

mysql>

爲了再次確認,退出MySQL後重新查看

mysql> exit
Bye
[root@localhost ~]# mysql -uroot -predhat test
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 13 to server version: 5.0.22

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql>

從結果發現,名字爲"Sunrier"小朋友的信息又回來了,真是太高興了.

2.MySQL下使用C的API實例(注:student爲我的MySQL數據庫test中先前已經創建的一個student表信息):

//dbproc.c

/*************************************************************       
    FileName : dbproc.c   
    FileFunc : MySQL數據庫事務操作     
    Version  : V0.1       
    Author   : Sunrier       
    Date     : 2012-06-19 
    Descp    : Linux下使用C語言訪問MySQL函數        
*************************************************************/   
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <mysql.h>

static MYSQL s_my_connection;
static int s_iDbconnected = 0;//數據庫連接標誌 連接時爲1,斷開時爲0

int mysql_login(char* pServer,char *pUser,char *pPassword,char *pDataBase)
{
	MYSQL *conn_ptr = NULL;
	int iRetCode = -1;
	unsigned int uiTimeOut = 7;

	if( s_iDbconnected )
		return 0;
		
	conn_ptr = mysql_init(&s_my_connection);
	if( !conn_ptr )
	{
		fprintf(stderr,"mysql_init failed ! \n");
		return EXIT_FAILURE;
	}

	iRetCode = mysql_options(&s_my_connection,MYSQL_OPT_CONNECT_TIMEOUT,(const char *)&uiTimeOut);
	if( iRetCode  )
	{
		fprintf(stderr,"MySQL Connection is timeout! \n");
		return EXIT_FAILURE;
	}
	
	conn_ptr = NULL;
	conn_ptr = mysql_real_connect(&s_my_connection,pServer,pUser,pPassword,pDataBase,0,NULL,0);
	if( conn_ptr )
	{
		printf("MySQL Connection success!\n");
		s_iDbconnected = 1;		
	}
	else
	{
		fprintf(stderr,"MySQL Connection failed!\n");
		if( mysql_errno(&s_my_connection) )
		{
			fprintf(stderr,"Connection error %d: %s!\n",mysql_errno(&s_my_connection),mysql_error(&s_my_connection));
			return EXIT_FAILURE;
		}
	}
	
	return EXIT_SUCCESS;
}


void mysql_logout( void )
{
	if( s_iDbconnected )
		mysql_close(&s_my_connection);//關閉連接  
	s_iDbconnected = 0 ;
}

//ucMode = 1啓動自動模式,一般爲默認模式
//ucMode = 0禁止autocommit模式
int mysql_commitmode(unsigned char ucMode)
{
	int iRetCode = -1;
	
	iRetCode = mysql_autocommit(&s_my_connection,ucMode);
	if( iRetCode )
	{
		fprintf(stderr,"Set autocommit %d-mode error ,sqlcode=[%d] : %s ",ucMode,mysql_errno(&s_my_connection),mysql_error(&s_my_connection));
		return EXIT_FAILURE;
	}
	else
	{
		return EXIT_SUCCESS;
	}
}
	

int mysql_proc( void )
{
	MYSQL *conn_ptr = NULL;
	MYSQL_RES *res_ptr = NULL;
	MYSQL_ROW sqlrow;
	int iTableRow = 0;
	int iRetCode = 1;
	char szSql[256];
	
	memset(szSql,0,sizeof(szSql));
	sprintf(szSql,"insert into student values(9,'Marry',23)");
	
	iRetCode = mysql_query(&s_my_connection,szSql);
	if( iRetCode )
	{
		fprintf(stderr,"insert error ,sqlcode=[%d] : %s ",mysql_errno(&s_my_connection),mysql_error(&s_my_connection));
		mysql_rollback(&s_my_connection);//回滾操作
		return EXIT_FAILURE;
	}
	
	mysql_commit(&s_my_connection);//提交操作(即手動提交)
	return EXIT_SUCCESS;
}

//demo.c

/*************************************************************       
    FileName : demo.c   
    FileFunc : MySQL數據庫事務的測試     
    Version  : V0.1       
    Author   : Sunrier       
    Date     : 2012-06-19  
    Descp    : Linux下使用C語言訪問MySQL函數        
*************************************************************/   
#include <stdio.h>

int main(int argc,char *argv[])
{
	int iRetCode = -1;
	char szServer[20] = "localhost";
	char szUser[20] = "Sunrier";
	char szPassword[20] = "redhat"
	char szDatabase[20] = "test";
	
	iRetCode = mysql_login(szServer,szUser,szPassword,szDatabase);
	
	if( iRetCode )
	{	
		system("service mysqld start");
		iRetCode = mysql_login(szServer,szUser,szPassword,szDatabase);
	}
	
	mysql_commitmode(0);//禁止autocommit模式
	
	iRetCode = mysql_proc();
	if( iRetCode )
	{
		printf("MySQL proc error !\n");
	}	
	 
	mysql_logout();
	
	return 0;
}

//makefile

#makefile
all:demo
demo:demo.c dbproc.c
	@gcc -I/usr/include/mysql $?  -L/usr/lib/mysql -lmysqlclient  -lz -lm -o demo
clean:
	@ls | grep -v ^makefile$$ | grep -v [.]c$$ | grep -v [.]h$$ | grep -v [.]sql$$ | xargs rm -rf
#makefile

[Sunrier@localhost MySql]$ ls
dbproc.c demo.c makefile
[Sunrier@localhost MySql]$ make
[Sunrier@localhost MySql]$ ls
dbproc.c demo demo.c makefile
[Sunrier@localhost MySql]$ ./demo
MySQL Connection success!
[Sunrier@localhost MySql]$

執行前後查看數據庫:

由於程序中設置了禁止autocommit模式,如想插入記錄成功則需要提交函數,撤消操作則要回滾函數.

執行前數據庫:

執行後數據庫:

mysql> select * from student;
+--------+---------+------+
| studno | fname   | age |
+--------+---------+------+
|      1 | Jack    |   67 |
|      2 | Tim     |   22 |
|      3 | Sunrier |   23 |
|      4 | Helen   |   26 |
|      5 | Tony    |   29 |
|      6 | Cherry |   30 |
|      7 | Nicky   |   22 |
|      8 | Jerry   |   21 |
|      9 | Marry   |   23 |
+--------+---------+------+
9 rows in set (0.00 sec)

mysql>

//student.sql


drop database if exists test;
create database test;
use test;
create table student
(
	studno integer auto_increment not null primary key,
	fname varchar(30),
	age integer
);

-- )engine=innodb charset=gb2312;
--insert into student values ('',"Sunrier",22);
--insert into student values ('',"Tom",23);
--insert into student values ('',"Jerry",21);

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