連接Access數(shù)據(jù)庫(kù)
string connStr = @"Data Source=D:/database.mdb; Provider=Microsoft.Jet.OleDb.4.0;"; //數(shù)據(jù)庫(kù)連接字符串 OleDbConnection conn = new OleDbConnection(connStr);
連接Oracle數(shù)據(jù)庫(kù)
//數(shù)據(jù)庫(kù)和客戶端在同一臺(tái)機(jī)器上 using System.Data.OracleClient; string connStr = "data source=orcl;user=user;password=pwd;"; OracleConnection conn = new OracleConnection(connStr); //客戶端和數(shù)據(jù)庫(kù)不在同一臺(tái)機(jī)器，可以使用下面的連接方式 using System.Data.OleDb; //HOST是Oracle數(shù)據(jù)庫(kù)服務(wù)器地址，PORT是Oracle數(shù)據(jù)庫(kù)端口，SERVICE_NAME是數(shù)據(jù)庫(kù)名稱 string connStr = "Provider=OraOLEDB.Oracle.1;Data Source=(DESCRIPTION =(ADDRESS_LIST =(ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521)))(CONNECT_DATA =(SERVICE_NAME = orcl)));User ID=message;Password=message;"; OleDbConnection conn = new OleDbConnection(connStr);
連接SqlServer數(shù)據(jù)庫(kù)
using System.Data.SqlClient; string connStr = "data source=127.0.0.1;initial catalog=database;user id=sa;pwd=sa"; SqlConnection conn = new SqlConnection(connStr);
連接數(shù)據(jù)庫(kù),并從數(shù)據(jù)庫(kù)中讀取數(shù)據(jù)后并輸出!
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data.SqlClient; namespace Login { class Program { static void Main(string[] args) { //新建一個(gè)數(shù)據(jù)庫(kù)連接 using(SqlConnection conn = new SqlConnection(GetConnectString())) { conn.Open();//打開(kāi)數(shù)據(jù)庫(kù) //Console.WriteLine("數(shù)據(jù)庫(kù)打開(kāi)成功!"); //創(chuàng)建數(shù)據(jù)庫(kù)命令 SqlCommand cmd = conn.CreateCommand(); //創(chuàng)建查詢語(yǔ)句 cmd.CommandText = "SELECT * FROM userinfo"; //從數(shù)據(jù)庫(kù)中讀取數(shù)據(jù)流存入reader中 SqlDataReader reader = cmd.ExecuteReader(); //從reader中讀取下一行數(shù)據(jù),如果沒(méi)有數(shù)據(jù),reader.Read()返回flase while (reader.Read()) { //reader.GetOrdinal("id")是得到ID所在列的index, //reader.GetInt32(int n)這是將第n列的數(shù)據(jù)以Int32的格式返回 //reader.GetString(int n)這是將第n列的數(shù)據(jù)以string 格式返回 int id = reader.GetInt32(reader.GetOrdinal("id")); string name = reader.GetString(reader.GetOrdinal("name")); string pwd = reader.GetString(reader.GetOrdinal("password")); int age = reader.GetInt32(reader.GetOrdinal("age")); string sex = reader.GetString(reader.GetOrdinal("sex")); string phone = reader.GetString(reader.GetOrdinal("phone")); string address = reader.GetString(reader.GetOrdinal("Address")); //格式輸出數(shù)據(jù) Console.Write("ID:{0},Name:{1},PWD:{2},Age:{3},Sex:{4},Phone{5},Address:{6}/n", id, name, pwd, age, sex, phone, address); } } Console.ReadKey(); } //得到一個(gè)數(shù)據(jù)庫(kù)連接字符串 static string GetConnectString() { return "Data Source=(local);Initial Catalog=db1;Integrated Security=SSPI;"; } } }
判斷數(shù)據(jù)庫(kù)中取出的字段值是否為空（NULL）
最近操作數(shù)據(jù)庫(kù)，需要判斷返回的字段值是否為空，在Google上搜索到三種方法。
1 通過(guò)System.DBNull判斷，網(wǎng)上大部分都使用這個(gè)方法。
DataTable dt; //假設(shè)字段為name, dt已經(jīng)保存了數(shù)據(jù) dt.rows[0]["name"] == System.DBNull.Value; //判斷第一行數(shù)據(jù)的name字段是否為空
2 通過(guò)IsNull判斷
DataTable dt; //假設(shè)字段為name, dt已經(jīng)保存了數(shù)據(jù) dt.rows[0].IsNull("name"); //判斷第一行數(shù)據(jù)的name字段是否為空 3 通過(guò)ToString() 判斷，這個(gè)方法我沒(méi)有試過(guò)。
DataTable dt; //假設(shè)字段為name, dt已經(jīng)保存了數(shù)據(jù) dt.rows[0]["name"].ToString() == ""; //判斷第一行數(shù)據(jù)的name字段是否為空
