！！C#交互操作SqlServer数据库 基本的增删改查

C#交互操作SqlServer数据库

 基本的增删改查


增 
using(SqlConnection conn=new SqlConnection("server=;database=;user=;pwd="))
{
conn.Open();
using(SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText="Insert into T_user (Username,Password,Errotimes) values(@Username,@Password,@Errotimes)";
cmd.Parameters.Add(new SqlParameter("@Username",Username));
cmd.Parameters.Add(new SqlParameter("@Password",Password));
cmd.Parameters.Add(new SqlParameter("@Errotimes",Errotimes));
cmd.ExecuteNonQuery();
}
}

 


删
using(SqlConnection conn=new SqlConnection("server=;database=;user=;pwd="))
{
conn.Open();
using(SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText="delete from T_user where id=@id ";
cmd.Parameters.Add(new SqlParameter("@id",id));

cmd.ExecuteNonQuery();
}
}

 

 

改
using(SqlConnection conn=new SqlConnection("server=;database=;user=;pwd="))
{
conn.Open();
using(SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText="Update _user set Username=@Username,Password=@Password,Errotimes=@Errotimes"
cmd.Parameters.Add(new SqlParameter("@Username",Username));
cmd.Parameters.Add(new SqlParameter("@Password",Password));
cmd.Parameters.Add(new SqlParameter("@Errotimes",Errotimes));
cmd.ExecuteNonQuery();
}
}

 

 

查询1 返回一行一列的查询
using(SqlConnection conn=new SqlConnection("server=;database=;user=;pwd="))
{
conn.Open();
using(SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText="select count(*) from T_user where name=@name";
cmd.Parameters.Add(new SqlParameter("@name",name));
cmd.ExecuteScalar();
}
}

 

 

查询2 “一般查询”（DataSet离线脱离数据库查询） 
using(SqlConnection conn=new SqlConnection("server=;database=;user=;pwd="))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = "select*from youdao where pwd=@pwd";
cmd.Parameters.Add(new SqlParameter("@pwd", txt.Text));
SqlDataAdapter adapter = new SqlDataAdapter(cmd);
DataSet dataset = new DataSet();
adapter.Fill(dataset);
DataTable table = dataset.Tables[0];
DataRowCollection rows = table.Rows;
for (int i = 0; i < rows.Count; i++) 
{
DataRow row = rows[i];
int Age = (int)row["age"];
string name = (string)row["name"];

}
}

}

 


查询三 “大数据 ”连接数据库查询 ExcuteReader();
using(SqlConnection conn=new SqlConnection("server=;database=;user=;pwd="))
{
conn.Open();
using(SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText="select*from T_user where name=@name";
cmd.Parameters.Add(new SqlParameter("@name",name));
using(SqlDataReader dr=cmd.ExecuteReader())
{ while(dr.Read())
{
string Name=dr.GetString(0);
int Age =dr.GetInt32(1); 
}

}
}
}