c连接mysql数据库
里的大部分代码参考了MySQL发行包里面的.c源文件，大家也可以去里面找找相关的代码，下面这段代码实现了连接到本地MySQL服务器上9tmd_bbs_utf8数据库，从数据表tbb_user中根据输入的userid取得该用户的用户名并打印输出到终端。
if defined(_WIN32) || defined(_WIN64)为了支持windows平台上的编译
#include <windows.h> #endif #include <stdio.h> #include <stdlib.h> #include "mysql.h"
我的机器上该文件在/usr/local/include/mysql下
定义MySQL数据库操作的宏，也可以不定义留着后面直接写进代码
define SELECT_QUERY "select username from tbb_user where userid = %d" int main(int argc, char **argv)char **argv 相当于 char *argv[] {
MYSQL mysql,*sock;定义数据库连接的句柄，它被用于几乎所有的MySQL函数
MYSQL_RES *res;查询结果集，结构类型
MYSQL_FIELD *fd ;包含字段信息的结构
MYSQL_ROW row ;存放一行查询结果的字符串数组
char qbuf[160];存放查询sql语句字符串
if (argc != 2) { //检查输入参数 fprintf(stderr,"usage : mysql_select <userid>\n\n"); exit(1); } mysql_init(&mysql); if (!(sock = mysql_real_connect(&mysql,"localhost","dbuser","dbpwd","9tmd_bbs_utf8",0,NULL,0))) { fprintf(stderr,"Couldn't connect to engine!\n%s\n\n",mysql_error(&mysql)); perror(""); exit(1); } sprintf(qbuf,SELECT_QUERY,atoi(argv[1])); if(mysql_query(sock,qbuf)) { fprintf(stderr,"Query failed (%s)\n",mysql_error(sock)); exit(1); } if (!(res=mysql_store_result(sock))) { fprintf(stderr,"Couldn't get result from %s\n", mysql_error(sock)); exit(1); } printf("number of fields returned: %d\n",mysql_num_fields(res)); while (row = mysql_fetch_row(res)) { printf("Ther userid #%d 's username is: %s\n", atoi(argv[1]),(((row[0]==NULL)&&(!strlen(row[0]))) ? "NULL" : row[0])) ; puts( "query ok !\n" ) ; } mysql_free_result(res); mysql_close(sock); exit(0); return 0;
为了兼容大部分的编译器加入此行
}
编译的时候，使用下面的命令
gcc -o mysql_select ./mysql_select.c -I/usr/local/include/mysql -L/usr/local/lib/mysql -lmysqlclient (-lz) (-lm) 后面两个选项可选，根据您的环境情况运行的时候，执行下面的命令
./mysql_select 1
将返回如下结果：
number of fields returned: 1 Ther userid #1 's username is: Michael query ok !
上面的代码我想大部分都能看明白，不明白的可以参考一下MySQL提供的有关C语言API部分文档，各个函数都有详细说明，有时间我整理一份常用的API说明出来。
B. 如何用C语言连接MYSQL数据库
1、配置ODBC数据源。
2、使用SQL函数进行连接。
对于1、配置数据源，配置完以后就可以编程操作数据库了。
对于2、使用SQL函数进行连接，参考代码如下：
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#include<windows.h>
#include<sql.h>
#include<sqlext.h>
void
main()
{
HENV
henv;
//环境句柄
HDBC
hdbc;
//数据源句柄
HSTMT
hstmt;
//执行语句句柄
unsigned
char
datasource[]="数据源名称";
//即源中设置的源名称
unsigned
char
user[]=
"用户名";
//数据库的帐户名
unsigned
char
pwd[]=
"密码";
//数据库的密码
unsigned
char
search[]="select
xm
from
stu
where
xh=0";
SQLRETURN
retcode;
//记录各SQL函数的返回情况
//
分配环境句柄
retcode=
SQLAllocEnv(&henv);
//
等介于
SQLAllocHandle(SQL_HANDLE_ENV,
SQL_NULL
,
&henv);
//
设置ODBC环境版本号为3.0
retcode=
SQLSetEnvAttr(henv,
SQL_ATTR_ODBC_VERSION,
(void*)SQL_OV_ODBC3,
0);
//
分配连接句柄
retcode=
SQLAllocConnect(henv,&hdbc);
//
等介于
SQLAllocHandle(SQL_HANDLE_DBC,
henv,
&hdbc);
//设置连接属性,登录超时为*rgbValue秒（可以没有）
//
SQLSetConnectAttr(hdbc,
SQL_LOGIN_TIMEOUT,
(SQLPOINTER)(rgbValue),
0);
//直接连接数据源
//
如果是windows身份验证，第二、三参数可以是
C. 用C语言怎么实现与数据库的连接
#include<mysql/mysql.h>
#include<stdio.h>
intmain()
{
MYSQL*conn;
MYSQL_RES*res;
MYSQL_ROWrow;
char*server="localhost";//本地连接
char*user="root";//
char*password="525215980";//mysql密码
char*database="student";//数据库名
char*query="select*fromclass";//需要查询的语句
intt,r;
conn=mysql_init(NULL);
if(!mysql_real_connect(conn,server,user,password,database,0,NULL,0))
{
printf("Errorconnectingtodatabase:%s ",mysql_error(conn));
}else{
printf("Connected... ");
}
t=mysql_query(conn,query);
if(t)
{
printf("Errormakingquery:%s ",mysql_error(conn));
}else{
printf("Querymade... ");
res=mysql_use_result(conn);
if(res)
{
while((row=mysql_fetch_row(res))!=NULL)
{
//printf("num=%d ",mysql_num_fields(res));//列数
for(t=0;t<mysql_num_fields(res);t++)
printf("%8s",row[t]);
printf(" ");
}
}
mysql_free_result(res);
}
mysql_close(conn);
return0;
}
(3)c连接mysql数据库扩展阅读
C语言使用注意事项：
1、指针是c语言的灵魂，一定要灵活的使用它：
（1）、指针的声明，创建，赋值，销毁等
（2）、指针的类型转换，传参，回调等
2、递归调用也会经常用到：
（1）、递归遍历树结构
（2）、递归搜索
D. Linux下C连接MySQL数据库错
skipping incompatible /usr/lib/mysql/libmysqlclient_r.a 这里是说这个库文件与当前系统的编译器gcc不一致，你需要确认一下是不是机器位数的问题
gcc -m32 -o test test.c `mysql_config --cflags --libs` 这样试试
E. C#连接mysql数据库如何实现多条件查询
给你一个稍微复杂一点的查询，我设计的
F. c语言怎么连接mysql数据库 代码
//vc工具中添加E:\WAMP\BIN\MYSQL\MYSQL5.5.8\LIB 路径
//在工程设置-》链接》库模块中添加 libmysql.lib
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <winsock.h>
#include "E:\wamp\bin\mysql\mysql5.5.8\include\mysql.h"
void main(){
MYSQL *conn;
MYSQL_RES *res;
MYSQL_ROW row;
char *server ="localhost";
char *user ="root";
char *password="";
char *database="test";
char sql[1024]="select * from chinaren";
conn=mysql_init(NULL);
if(!mysql_real_connect(conn,server,user,password,database,0,NULL,0)){
fprintf(stderr,"%s\n",mysql_error(conn));
exit(1);
}
if(mysql_query(conn,sql)){
fprintf(stderr,"%s\n",mysql_error(conn));
exit(1);
}
res=mysql_use_result(conn);
while((row = mysql_fetch_row(res))!=NULL){
printf("%s\n",row[2]);
}
mysql_free_result(res);
mysql_close(conn);
}
===============================
#if defined(_WIN32) || defined(_WIN64) //为了支持windows平台上的编译
#include <windows.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include "mysql.h"
//定义数据库操作的宏，也可以不定义留着后面直接写进代码
#define SELECT_QUERY "show tables;"
int main(int argc, char **argv) //char **argv 相当于 char *argv[]
{
MYSQL mysql,*handle; //定义数据库连接的句柄，它被用于几乎所有的MySQL函数
MYSQL_RES *result; //查询结果集，结构类型
MYSQL_FIELD *field ; //包含字段信息的结构
MYSQL_ROW row ; //存放一行查询结果的字符串数组
char querysql[160]; //存放查询sql语句字符串
//初始化
mysql_init(&mysql);
//连接数据库
if (!(handle = mysql_real_connect(&mysql,"localhost","user","pwd","dbname",0,NULL,0))) {
fprintf(stderr,"Couldn't connect to engine!\n%s\n\n",mysql_error(&mysql));
}
sprintf(querysql,SELECT_QUERY,atoi(argv[1]));
//查询数据库
if(mysql_query(handle,querysql)) {
fprintf(stderr,"Query failed (%s)\n",mysql_error(handle));
}
//存储结果集
if (!(result=mysql_store_result(handle))) {
fprintf(stderr,"Couldn't get result from %s\n", mysql_error(handle));
}
printf("number of fields returned: %d\n",mysql_num_fields(result));
//读取结果集的内容
while (row = mysql_fetch_row(result)) {
printf("table: %s\n",(((row[0]==NULL)&&(!strlen(row[0]))) ? "NULL" : row[0]) ) ;
}
//释放结果集
mysql_free_result(result);
//关闭数据库连接
mysql_close(handle);
system("PAUSE");
//为了兼容大部分的编译器加入此行
return 0;
}
G. 用C#.net连接MYSQL，怎么连接还要安装什么吗急！！！
连接MYSQL数据库的方法及示例
方法一：
使用MYSQL推出的MySQL
Connector/Net
is
an
ADO.NET
driver
for
MySQL
该组件为MYSQL为ADO.NET访问MYSQL数据库设计的.NET访问组件。
安装完成该组件后，引用命名空间MySql.Data.MySqlClient;
使用命令行编译时：csc
/r:MySql.Data.dll
test.cs
方法二：
通过ODBC访问MYSQL数据库
访问前要先下载两个组件：odbc.net和MYSQL的ODBC驱动(MySQL
Connector/ODBC
(MyODBC)
driver)目前为3.51版
安装完成后，即可通过ODBC访问MYSQL数据库
方法三：
使用CoreLab推出的MYSQL访问组件，面向.NET
安装完成后，引用命名空间：CoreLab.MySql;
使用命令编译时：csc
/r:CoreLab.MySql.dll
test.cs
以下为访问MYSQL数据库实例
编译指令：csc
/r:CoreLab.MySql.dll
/r:MySql.Data.dll
test.cs
using
System;
using
System.Net;
using
System.Text;
using
CoreLab.MySql;
using
System.Data.Odbc;
using
MySql.Data.MySqlClient;
class
ConnectMySql
{
public
void
Connect_CoreLab()
{
string
c;
MySqlConnection
mycn
=
new
MySqlConnection(constr);
mycn.Open();
MySqlCommand
mycm
=
new
MySqlCommand("select
*
from
shop",mycn);
MySqlDataReader
msdr
=
mycm.ExecuteReader();
while(msdr.Read())
{
if
(msdr.HasRows)
{
Console.WriteLine(msdr.GetString(0));
}
}
msdr.Close();
mycn.Close();
}
public
void
Connect_Odbc()
{
//string
MyC;
string
MyC
+
"SERVER=localhost;"
+
"DATABASE=test;"
+
"UID=root;"
+
"PASSWORD=qing;"
+
"OPTION=3";
OdbcConnection
MyConn
=
new
OdbcConnection(MyConString);
MyConn.Open();
OdbcCommand
mycm
=
new
OdbcCommand("select
*
from
hello",MyConn);
OdbcDataReader
msdr
=
mycm.ExecuteReader();
while(msdr.Read())
{
if
(msdr.HasRows)
{
Console.WriteLine(msdr.GetString(0));
}
}
msdr.Close();
MyConn.Close();
}
public
void
Connect_Net()
{
string
myC;
MySqlConnection
mycn
=
new
MySqlConnection(myConnectionString);
mycn.Open();
MySqlCommand
mycm
=
new
MySqlCommand("select
*
from
hello",mycn);
MySqlDataReader
msdr
=
mycm.ExecuteReader();
while(msdr.Read())
{
if
(msdr.HasRows)
{
Console.WriteLine(msdr.GetString(0));
}
}
msdr.Close();
mycn.Close();
}
public
static
void
Main()
{
ConnectMySql
ms
=
new
ConnectMySql();
ms.Connect_CoreLab();
ms.Connect_Odbc();
Connect_Net();
}
}
H. c#利用mysql connector net怎么连接mysql数据库
(1)首先需要下载C#访问MySQL数据库的ADO.NET驱动程序
mysql-connector-net-6.3.8.msi
(2)安装mysql-connector-net
然后直接在Windows操作系统安装 mysql-connector-net-6.3.8.msi
(3)封装数据库访问组件DbConnectionMySQL
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/// <summary>
/// MySQL数据库
/// 版本 mysql-connector-net-6.3.8.msi
/// </summary>
[Serializable]
public class DbConnectionMySQL : DbConnectionWrapper
{
public DbConnectionMySQL(string pConnectionString)
: base(pConnectionString)
{
this.m_dbconn = new MySqlConnection(pConnectionString);
this.m_DbConnState = DbConnState.Free;
}
//--
public override DbDataAdapter GetDbDataAdapter()
{
return new MySqlDataAdapter();
}
public override DbDataAdapter GetDbDataAdapter(DbCommand dbCommand)
{
return new MySqlDataAdapter(dbCommand as MySqlCommand);
}
public override DbCommand GetDbCommand()
{
return new MySqlCommand();
}
public override DbConnection GetDbConnection()
{
return new MySqlConnection();
}
public override DbCommandBuilder GetDbCommandBuilder()
{
return new MySqlCommandBuilder();
}
public override DataProviderType GetCurrentDataProviderType()
{
return DataProviderType.Sql;
}
public override bool IsExistsTable(string TableName, string UserName)
{
#region information
bool rbc = false; //TABLES表中去查询 table_name
string dSql = "select * from TABLES where table_name='" + TableName + "'";
DataSet ds = this.ExecuteDataSet(dSql);
if (ds != null)
{
if (ds.Tables[0].Rows.Count > 0)
{
rbc = true;
}
else
{
rbc = false;
}
}
else
{
rbc = false;
}
return rbc;
#endregion
}
public override bool IsExistsField(string FieldName, string TableName)
{
#region information
bool rbc = false;
string dSql = "";
dSql = "select * from " + TableName + " where 1<>1";
DataSet ds = this.ExecuteDataSet(dSql);
if (ds != null)
{
DataTable dt = ds.Tables[0];
for (int j = 0; j < dt.Columns.Count; j++)
{
if (dt.Columns[j].ColumnName.ToString().ToUpper() == FieldName.ToString().ToUpper())
{
rbc = true;
goto Return_End;
}
}
dt.Dispose();
dt = null;
}
ds.Dispose();
ds = null;
Return_End:
return rbc;
#endregion
}
public override char ParameterChar
{
get
{
return ':'; //SQLite的参数符号为:
}
}
public override DbParameter CreateParameter(string name, object value)
{
return new MySqlParameter(name, value);
}
public override DbParameter CreateParameter(string name)
{
DbParameter dbp = new MySqlParameter();
dbp.ParameterName = name;
return dbp;
}
public override DbParameter CreateParameter(string name, DbType dbtype, object value)
{
DbParameter dbp = new MySqlParameter();
dbp.ParameterName = name;
dbp.Value = value;
dbp.DbType = dbtype;
return dbp;
}
public override DbParameter CreateParameter(string name, DbType dbtype, int size, object value)
{
DbParameter dbp = new MySqlParameter();
dbp.ParameterName = name;
dbp.Value = value;
dbp.DbType = dbtype;
dbp.Size = size;
return dbp;
}
}
（4)客户端开发实例
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public void TestCShape_MySQL()
{
string constr = "server=localhost;User Id=root;password=root;Database=xp_users";
DbConnectionWrapper dbw = new DbConnectionMySQL(constr);
bool rbc=dbw.TestConnection();
this.Context.Response.Write(rbc);
string x = "";
//删除语句
x = "delete from xp_users";
if (dbw.ExecuteQuery(x) > 0)
{
this.Context.Response.Write("删除语句成功!下面是<a href="https://www..com/s?wd=SQL%E8%AF%AD%E5%8F%A5&tn=44039180_cpr&fenlei=-bIi4WUvYETgN-" target="_blank" class="-highlight">SQL语句</a>" + x);
}
//插入语句
x = "insert into xp_users(gid,uid,uname,sex,email,pwd) values('";
x += "1','hsg77','何XXX',1,'[email protected]','1')";
if (dbw.ExecuteQuery(x) > 0)
{
this.Context.Response.Write("插入语句成功!下面是<a href="https://www..com/s?wd=SQL%E8%AF%AD%E5%8F%A5&tn=44039180_cpr&fenlei=-bIi4WUvYETgN-" target="_blank" class="-highlight">SQL语句</a>"+x);
}
//查询语句
DataTable dt = dbw.ExecuteDataTable("select * from xp_users");
if (dt != null && dt.Rows.Count > 0)
{
this.Context.Response.Write("用户数:"+dt.Rows.Count);
}
if (dt != null)
{
dt.Dispose();
dt = null;
}
dbw.Dispose();
dbw = null;
}
I. C语言怎样连接mysql数据库
mysql是有c语言接口的，安装相应库后就可以链接了，一般连接mysql的函数是mysql_connect或者mysql_real_connect(大概就是这么拼的吧。。。）可以使用mysql_query执行sql语句
J. C#连接mysql数据库，怎么设置超时时间
MySQL查询超时的设置方法
为了优化OceanBase的query timeout设置方式，特调研MySQL关于timeout的处理，记录如下。
[plain]
mysql> show variables like '%time%';
+----------------------------+-------------------+
| Variable_name | Value |
+----------------------------+-------------------+
| connect_timeout | 10 |
| datetime_format | %Y-%m-%d %H:%i:%s |
| delayed_insert_timeout | 300 |
| flush_time | 1800 |
| innodb_lock_wait_timeout | 50 |
| innodb_old_blocks_time | 0 |
| innodb_rollback_on_timeout | OFF |
| interactive_timeout | 28800 |
| lc_time_names | en_US |
| lock_wait_timeout | 31536000 |
| long_query_time | 10.000000 |
| net_read_timeout | 30 |
| net_write_timeout | 60 |
| slave_net_timeout | 3600 |
| slow_launch_time | 2 |
| system_time_zone | |
| time_format | %H:%i:%s |
| time_zone | SYSTEM |
| timed_mutexes | OFF |
| timestamp | 1366027807 |
| wait_timeout | 28800 |
+----------------------------+-------------------+
21 rows in set, 1 warning (0.00 sec)
重点解释其中几个参数：
connect_timeout:
The number of seconds that the mysqld server waits for a connect packet before respondingwith Bad handshake. The default value is 10 seconds as of MySQL 5.1.23 and 5 seconds before that. Increasing the connect_timeout value might help if clients frequently encounter errors of the form Lost connection to MySQL server at ‘XXX’, system error: errno.
解释：在获取链接时，等待握手的超时时间，只在登录时有效，登录成功这个参数就不管事了。主要是为了防止网络不佳时应用重连导致连接数涨太快，一般默认即可。
interactive_timeout:
The number of seconds the server waits for activity on an interactive connection before closing it. An interactive client is defined as a client that uses the CLIENT_INTERACTIVE option to mysql_real_connect(). See alsowait_timeout.
解释：一个持续SLEEP状态的线程多久被关闭。线程每次被使用都会被唤醒为acrivity状态，执行完Query后成为interactive状态，重新开始计时。wait_timeout不同在于只作用于TCP/IP和Socket链接的线程，意义是一样的。
MySQL可以配置连接的超时时间，这个时间如果做得太长，甚至到了10min，那么很可能发生这种情况，3000个链接都被占满而且sleep在哪，新链接进不来，导致无法正常服务。因此这个配置尽量配置一个符合逻辑的值，60s或者120s等等。
说人话：
命令行下面敲一个命令后，直至下一个命令到来之前的时间间隔为interactive_time，如果这个时间间隔超过了interactive_timeout，则连接会被自动断开，下一个命令失败。不过一般的mysql客户端都有自动重连机制，下一个命令会在重连后执行。
[sql]
mysql> set interactive_timeout = 1;
Query OK, 0 rows affected (0.00 sec)
mysql> show session variables like '%timeout%';
+----------------------------+----------+
| Variable_name | Value |
+----------------------------+----------+
| connect_timeout | 10 |
| interactive_timeout | 1 |
| wait_timeout | 28800 |
+----------------------------+----------+
10 rows in set (0.00 sec)
=====
[sql]
mysql> set wait_timeout = 1;
Query OK, 0 rows affected (0.00 sec)
【去泡杯茶，等会儿】
mysql> show session variables like '%timeout%';
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id: 7
Current database: *** NONE ***
+----------------------------+----------+
| Variable_name | Value |
+----------------------------+----------+
| connect_timeout | 10 |
| interactive_timeout | 28800 |
| wait_timeout | 28800 |
+----------------------------+----------+
10 rows in set (0.01 sec)
wait_timeout:
The number of seconds the server waits for activity on a noninteractive connection (连接上没有活动命令，可能是客户端喝咖啡去了。)before closing it. Before MySQL 5.1.41, this timeout applies only to TCP/IP connections, not to connections made through Unix socket files, named pipes, or shared memory.
On thread startup, the session wait_timeout value is initialized from the global wait_timeout value or from the global interactive_timeout value, depending on the type of client
这里顺带解释一下什么是non-interactive connection
> Non-Interactive Commands
Just do a quick look up on a table without logging into the client, running the query then logging back out again.
You can instead just type one line using the ' -e ' flag.
[sql]
c:\mysql\bin\mysql -u admin -p myDatabase -e 'SELECT * FROM employee'
net_read_timeout / net_write_timeout
The number of seconds to wait for more data from a connection before aborting the read. Before MySQL 5.1.41, this timeout applies only to TCP/IP connections, not to connections made through Unix socket files, named pipes, or shared memory. When the server is reading from the client, net_read_timeout is the timeout value controlling when to abort. When the server is writing to the client, net_write_timeout is the timeout value controlling when to abort. See also slave_net_timeout.
On Linux, the NO_ALARM build flag affects timeout behavior as indicated in the description of the net_retry_count system variable.
解释：这个参数只对TCP/IP链接有效，分别是数据库等待接收客户端发送网络包和发送网络包给客户端的超时时间，这是在Activity状态下的线程才有效的参数
JDBC setQueryTimeout函数：
为了避免查询出现死循环，或时间过长等现象，而导致线程阻塞，在获得Statement的实例后，stmt.setQueryTimeout(10); 避免因为查询导致程序出现线程阻塞。
但昨天发现程序出现了，“ORA-01013: 用户请求取消当前的操作”的异常。手工执行出错SQL语句发现，这个语句耗时20多秒。因为setQueryTimeout(10)，所以还没有执行完查询语句就抛出异常了。使用setQueryTimeout(10)时一定要把时间设置的长一些，如60秒以上。只要不导致线程长期阻塞，就可以。太短了容易抛出，“ORA-01013: 用户请求取消当前的操作”的异常
JDBC实现setQueryTimeout的原理：
[java]
class IfxCancelQueryImpl extends TimerTask
implements IfmxCancelQuery
{
IfxStatement stmt;
Timer t = null;
public void startCancel(IfxStatement paramIfxStatement, int paramInt)
throws Exception
{
this.stmt = paramIfxStatement;
this.t = new Timer(true);
this.t.schele(this, paramInt * 1000);
}
public void run()
{
try
{
this.stmt.cancel();
this.t.cancel();
}
catch (SQLException localSQLException)
{
this.t.cancel();
throw new Error(localSQLException.getErrorCode() + ":" + localSQLException.getMessage());
}
}
}