c#mysql操作
利用数据库提供的动态链接库MySql.Data.dll进行操作。MySql.Data.dll提供以下8个类：
- MySqlConnection: 连接MySQL服务器数据库。
- MySqlCommand:执行一条sql语句。
- MySqlDataReader: 包含sql语句执行的结果，并提供一个方法从结果中阅读一行。
- MySqlTransaction: 代表一个SQL事务在一个MySQL数据库。
- MySqlException: MySQL报错时返回的Exception。
- MySqlCommandBuilder: Automatically generates single-table commands used to reconcile changes made to a DataSet with the associated MySQL database.
- MySqlDataAdapter: Represents a set of data commands and a database connection that are used to fill a data set and update a MySQL database.
- MySqlHelper: Helper class that makes it easier to work with the provider.
建立连接(MySqlConnection类)
using MySql.Data.MySqlClient; String connetStr = "server=127.0.0.1;port=3306;user=root;password=root; database=minecraftdb;"; // server=127.0.0.1/localhost 代表本机，端口号port默认是3306可以不写 MySqlConnection conn = new MySqlConnection(connetStr); try { conn.Open();//打开通道，建立连接，可能出现异常,使用try catch语句 Console.WriteLine("已经建立连接"); //在这里使用代码对数据库进行增删查改 } catch (MySqlException ex) { Console.WriteLine(ex.Message); } finally { conn.Close(); }增删查改的代码(MySqlCommand类、MySqlDataReader类)
ExecuteReader——用于查询数据库。查询结果是返回MySqlDataReader对象，MySqlDataReader包含sql语句执行的结果，并提供一个方法从结果中阅读一行。
ExecuteNonQuery——用于插入、更新和删除数据。
ExecuteScalar——用于查询数据时，返回查询结果集中第一行第一列的值，即只返回一个值。
(1) 查询
a.查询条件固定
string sql= "select * from user"; MySqlCommand cmd = new MySqlCommand(sql,conn); MySqlDataReader reader =cmd.ExecuteReader();//执行ExecuteReader()返回一个MySqlDataReader对象 while (reader.Read())//初始索引是-1，执行读取下一行数据，返回值是bool { //Console.WriteLine(reader[0].ToString() + reader[1].ToString() + reader[2].ToString()); //Console.WriteLine(reader.GetInt32(0)+reader.GetString(1)+reader.GetString(2)); Console.WriteLine(reader.GetInt32("userid") + reader.GetString("username") + reader.GetString("password"));//"userid"是数据库对应的列名，推荐这种方式 }b.查询条件不固定
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//string sql = "select * from user where username='"+username+"' and password='"+password+"'"; //我们自己按照查询条件去组拼 string sql = "select * from user where username=@para1 and password=@para2";//在sql语句中定义parameter，然后再给parameter赋值 MySqlCommand cmd = new MySqlCommand(sql, conn); cmd.Parameters.AddWithValue("para1", username); cmd.Parameters.AddWithValue("para2", password); MySqlDataReader reader = cmd.ExecuteReader(); if (reader.Read())//如果用户名和密码正确则能查询到一条语句，即读取下一行返回true { return true; }c.需要查询返回一个值
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string sql = "select count(*) from user"; MySqlCommand cmd = new MySqlCommand(sql, conn); Object result=cmd.ExecuteScalar();//执行查询，并返回查询结果集中第一行的第一列。所有其他的列和行将被忽略。select语句无记录返回时，ExecuteScalar()返回NULL值 if (result != null) { int count = int.Parse(result.ToString()); }(2) 插入、删除、更改
string sql = "insert into user(username,password,registerdate) values('啊宽','123','"+DateTime.Now+"')"; //string sql = "delete from user where userid='9'"; //string sql = "update user set username='啊哈',password='123' where userid='8'"; MySqlCommand cmd = new MySqlCommand(sql,conn); int result =cmd.ExecuteNonQuery();//3.执行插入、删除、更改语句。执行成功返回受影响的数据的行数，返回1可做true判断。执行失败不返回任何数据，报错，下面代码都不执行事务(MySqlTransaction类)
String connetStr = "server=127.0.0.1;user=root;password=root;database=minecraftdb;"; MySqlConnection conn = new MySqlConnection(connetStr); conn.Open();//必须打开通道之后才能开始事务 MySqlTransaction transaction = conn.BeginTransaction();//事务必须在try外面赋值不然catch里的transaction会报错:未赋值 Console.WriteLine("已经建立连接"); try { string date = DateTime.Now.Year + "-" + DateTime.Now.Month + "-" + DateTime.Now.Day; string sql1= "insert into user(username,password,registerdate) values('啊宽','123','" + date + "')"; MySqlCommand cmd1 = new MySqlCommand(sql1,conn); cmd1.ExecuteNonQuery(); string sql2 = "insert into user(username,password,registerdate) values('啊宽','123','" + date + "')"; MySqlCommand cmd2 = new MySqlCommand(sql2, conn); cmd2.ExecuteNonQuery(); } catch (MySqlException ex) { Console.WriteLine(ex.Message); transaction.Rollback();//事务ExecuteNonQuery()执行失败报错，username被设置unique conn.Close(); } finally { if (conn.State != ConnectionState.Closed) { transaction.Commit();//事务要么回滚要么提交，即Rollback()与Commit()只能执行一个 conn.Close(); } }转载https://www.cnblogs.com/DonYao/p/8438375.html
备注：
string str = "Host=localhost;User ID=root;Password=;Port = 3306;DataBase=animals;Charset=utf8;";
MySqlConnection conn = new MySqlConnection(str);
conn.Open();//
////拿到数据库并打开连接
//string sql = "select *from student";
//MySqlCommand cmd = new MySqlCommand(sql, conn);
//MySqlDataAdapter mda = new MySqlDataAdapter(cmd);
//DataSet ds = new DataSet();
//mda.Fill(ds);
//dataGridView1.DataSource = ds.Tables[0];
////MySqlDataReader dr = cmd.ExecuteReader();
//conn.Close();
/*1.访问数据库的五大步骤
2.拿到要发送的sql语句
3.执行 sql 语句
4.拿到执行后的聚过
5.关闭连接 切记关闭连接
*/
////1 拿到数据库的连接 并打开连接
//string url = "User ID=root;Password=;Host=localhost;Port=3306;Database=xx;charset=xx;";
//MySqlConnection con = new MySqlConnection(url);
//con.Open();
////2.要拿到要发送的sql语句
//string sql = "select id from student where name='kobe'";
//MySqlCommand com = new MySqlCommand(sql, con);
//// 3 执行 sql 语句
//MySqlDataReader reader = com.ExecuteReader();
//reader.Read();// Read() 每次调用 都会从结果集中返回一行数据
//reader.GetInt32(0);
/*1.访问数据库的五大步骤
2.拿到要发送的sql语句
3.执行 sql 语句
4.拿到执行后的聚过
5.关闭连接 切记关闭连接
*/
//1 拿到数据库的连接 并打开连接
string url = "User ID=root;Password=;Host=localhost;Port=3306;Database=students;";
MySqlConnection con = new MySqlConnection(url);
con.Open();
//2.要拿到要发送的sql语句
string sql = "select *from student where name='kobe'";
MySqlCommand com = new MySqlCommand(sql, con);
// 3 执行 sql 语句
MySqlDataReader reader = com.ExecuteReader();
reader.Read();// Read() 每次调用 都会从结果集中返回一行数据
//reader.GetInt32(0);
Console.WriteLine(reader.GetInt32(0));
con.Close();
////对数据库进行 增 删 改 查
////1 拿到数据库的连接 并打开连接
//string url = "User ID=root;Password=root;Host=localhost;Port=3306;Database=students;";
//MySqlConnection con = new MySqlConnection(url);
//con.Open();
//string sql = "insert into student values(11,'hahahaha','man',6)";//添加信息
//MySqlCommand cmd = new MySqlCommand(sql, con);
//int result = cmd.ExecuteNonQuery();
//Console.WriteLine("数据库打开结果："+result);
//con.Close();
public static bool FindStudent(string name)
{
bool b = false;
string url = "User ID=root;Password=root;Host=localhost;Port=3306;Database=students;";
MySqlConnection con = new MySqlConnection(url);
con.Open();
string sql = "select *from studnet where name='{0}' ";
sql = string.Format(sql, name);
// Console.WriteLine(sql);
MySqlCommand cmd = new MySqlCommand(sql, con);
MySqlDataReader reader = cmd.ExecuteReader();
b = reader.Read();
return b;
}