关于SqlServer的连接字串

1  SqlServer的连接字串

    通常格式是： "server=localhost, portnum;uid=sa;pwd=password;database=master";

    sqlserver的标准端口是1433，如果安装的sqlserver使用的是这个标准端口，则上边的字串可以省略这个端口，则连接字串变成：

    "server=localhost, portnum;uid=sa;pwd=password;database=master";

2  数据库通常选择master, 查看数据库结构：

    

 

3  使用数据库时，务必要先选择数据库，否则会报以下错误：

    Invalid object name 'dbo.course'.

    使用数据库前，先使用 USE [KDemo]选择数据库，然后再对数据库进行相应操作。

string sql = "USE [KDemo];select count(*) from [dbo].[course]";

4   正确的写法，参考代码：

 private static void TestADONET()
 {
     //server = 服务器名,portname; database = 库名; uid = sa; pwd = 123456;
     //server ={0}; database = {1}; uid = {2}; pwd = {3};
     //string s = "Data Source=(localdb)\\MSSQLLocalDB;Initial Catalog=master;Integrated Security=True;Connect Timeout=30;Encrypt=False;";
     //string s = "server=127.0.0.1, 5433;uid=sa;pwd=Ikeqiang$1;database=master";
     string s = "server=localhost, 5433;uid=sa;pwd=yourpassword;database=master";
     SqlConnection conn = new SqlConnection(s);
    
     SqlCommand cmd = new SqlCommand();
     SqlDataAdapter sda = new SqlDataAdapter();
     DataSet ds = new DataSet();
     //select KDemo and then select table
     string sql = "USE [KDemo];select count(*) from [dbo].[course]";
     cmd.CommandText = sql;
     cmd.Connection = conn;
     try
     {
         conn.Open();
         object o = cmd.ExecuteScalar();
         int n = (int)o;
     }
     catch(Exception ex)
     {
         string msg = ex.Message;
     }
     finally
     { 
         conn.Close(); 
     }
 }

5  推荐查询官方文档

    https://learn.microsoft.com/en-us/sql/database-engine/configure-windows/configure-a-server-to-listen-on-a-specific-tcp-port?view=sql-server-ver16