C#连接数据库-曾,删,改,查

连接数据库

static void Main(string[] args) { //SqlConnection conn = new SqlConnection();//实例化 //conn.ConnectionString = "server=.;database=mydb;uid=sa;pwd=123";//初始化-----可以用下面一条语句执行 SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123"); Console.WriteLine(conn.State); conn.Open();//打开数据库连接 Console.WriteLine(conn.State); conn.Close();//关闭数据库连接 Console.WriteLine(conn.State); }

连接数据库并插入数据

static void Main(string[] args) { SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123"); conn.Open(); SqlCommand cmd = new SqlCommand(); cmd.Connection = conn;//初始化,通过conn数据对象连接数据库 cmd.CommandText = "insert into info values('p005','学生','0','n001','1990-02-1')";//""内为SQL语句 cmd.ExecuteNonQuery(); conn.Close(); Console.WriteLine("OK"); }

连接数据库并修改数据

public static void Main(string[] args) { SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123"); conn.Open(); SqlCommand cmd = new SqlCommand(); cmd.Connection = conn; cmd.CommandText = "update info set name='学员' where code='p005'"; cmd.ExecuteNonQuery(); conn.Close(); }

连接数据库并删除数据

public static void Main(string[] args) { SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123"); conn.Open(); SqlCommand cmd = conn.CreateCommand(); cmd.CommandText = "delete from info where code='p005'"; cmd.ExecuteNonQuery(); conn.Close(); }

 

 连接数据库查询数据

static void Main(string[] args) { SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123"); conn.Open(); SqlCommand cmd = conn.CreateCommand(); cmd.CommandText = "select * from info"; SqlDataReader r = cmd.ExecuteReader();//查询语句用ExecuteReader返回SqlDataReader类 while (r.Read()) { Console.WriteLine(r[0].ToString()+r[1].ToString()+r[2].ToString()); } conn.Close(); }

 

 

 案例:用户登录实现

public static void Main(string[] arges) { Console.Write("用户名:"); string uid = Console.ReadLine(); Console.Write("密码:"); string pwd = Console.ReadLine(); SqlConnection conn = new SqlConnection("server=.;database=mydb;uid=sa;pwd=123"); conn.Open(); SqlCommand cmd = conn.CreateCommand(); cmd.CommandText = "select * from login where username='"+uid+"' and password='"+pwd+"'"; SqlDataReader r = cmd.ExecuteReader(); if (r.HasRows == false) { Console.WriteLine("嗯哼,不对"); } else { Console.WriteLine("嗯哼,正确"); } conn.Close(); }

*** .HasRows()与.read()区别:HasRows只关系读数据库中的数据是否可行,而不执行读的操作.Read是执行读的操作看是否执行成功.二者都返回一个bool行的变量.***

转载于:https://www.cnblogs.com/IT1517/p/4768325.html

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