问一下数据库取值问题 我想取一个数据库中同一列不同记录的值,乍么取呀?我会取同一记录不同列的值,但这样我就不会了,请高手指教!!最好给些代码在线等 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 while(dr.Read())dr["列名"].ToString() 如果用DataTable的话:int k=dt.Rows.Count;String[] myValue=new String[k]for(int i=0;i<k;i++){String[i]=Convert.ToString(dt.Rows[i][2]); //取得所有行的,第二列的值.存在字符串数中} sqlconncetion...conn.open()sqlcommand...sqldataread dr=cmd.ExecuteReader();while(dr.read()){ ...=dr["数据库字段"]}conn.Close();不要给大钻石分了 他用不到的 public float GetNSFBL(out float N2,out float N3) { OleDbConnection dbCntGuize; string sqlstr; string dbpvd; string dbname; dbpvd = "Provider=Microsoft.Jet.OLEDB.4.0"; dbname = "Data Source = " + ParentDir(Directory.GetCurrentDirectory(), 4) + "\\施肥数据库\\果类施肥.mdb"; dbCntGuize = new OleDbConnection(dbpvd + ";" + dbname); dbCntGuize.Open(); //打开“施肥比例1”表 OleDbCommand dbcmd; sqlstr = "select * from 施肥比例1"; dbcmd = new OleDbCommand(sqlstr, dbCntGuize); OleDbDataReader myreader = dbcmd.ExecuteReader(); float N1 = 0; N2 = 0; N3 = 0; while (myreader.Read()) { N1 = myreader["N"]; N2 = myreader["N"]; N3 = myreader["N"]; } myreader.Close(); return N1; }循环里出错,why???说是无法将object 转换为float。 N1,N2,N3定义的都是float类型后面的是 系统返回的object类型。当然又错了 你可以这样!!!!!public float GetNSFBL(out float N2,out float N3) { OleDbConnection dbCntGuize; string sqlstr; string dbpvd; string dbname; dbpvd = "Provider=Microsoft.Jet.OLEDB.4.0"; dbname = "Data Source = " + ParentDir(Directory.GetCurrentDirectory(), 4) + "\\施肥数据库\\果类施肥.mdb"; dbCntGuize = new OleDbConnection(dbpvd + ";" + dbname); dbCntGuize.Open(); //打开“施肥比例1”表 OleDbCommand dbcmd; sqlstr = "select * from 施肥比例1"; dbcmd = new OleDbCommand(sqlstr, dbCntGuize); OleDbDataReader myreader = dbcmd.ExecuteReader(); object N1 = 0; N2 = 0; N3 = 0; while (myreader.Read()) { N1 = myreader["N"]; N2 = myreader["N"]; N3 = myreader["N"]; } myreader.Close(); return N1; }测试过了 没错!!!! 主程序开机隐藏问题 怎么让lable1.text显示char[ ]a里的内容? 把成功和失败的数据ID和原因,记录在log.csv里。请指教! winform 问题 集锦 关于冒泡排序的一点! 请教C#如何用PerformanceCounter获取网络磁盘的读写速度信息 windows 服务中插入数据库 請高手批評指正!100分!! C#中怎样自定义打开文件的对话框? 请教一个奇葩问题:MDI窗口中MdiClient背后的窗体背景色问题 如果你正了路过,事又不急的话,或许你可以帮帮我呵... 关于delegate 的问题
dr["列名"].ToString()
int k=dt.Rows.Count;
String[] myValue=new String[k]
for(int i=0;i<k;i++)
{
String[i]=Convert.ToString(dt.Rows[i][2]); //取得所有行的,第二列的值.存在字符串数中
}
conn.open()
sqlcommand...
sqldataread dr=cmd.ExecuteReader();
while(dr.read())
{
...=dr["数据库字段"]
}
conn.Close();
不要给大钻石分了 他用不到的
{
OleDbConnection dbCntGuize;
string sqlstr;
string dbpvd;
string dbname;
dbpvd = "Provider=Microsoft.Jet.OLEDB.4.0";
dbname = "Data Source = " + ParentDir(Directory.GetCurrentDirectory(), 4) + "\\施肥数据库\\果类施肥.mdb";
dbCntGuize = new OleDbConnection(dbpvd + ";" + dbname);
dbCntGuize.Open(); //打开“施肥比例1”表
OleDbCommand dbcmd;
sqlstr = "select * from 施肥比例1";
dbcmd = new OleDbCommand(sqlstr, dbCntGuize);
OleDbDataReader myreader = dbcmd.ExecuteReader(); float N1 = 0;
N2 = 0;
N3 = 0;
while (myreader.Read())
{
N1 = myreader["N"];
N2 = myreader["N"];
N3 = myreader["N"];
}
myreader.Close(); return N1; }循环里出错,why???说是无法将object 转换为float。
public float GetNSFBL(out float N2,out float N3)
{
OleDbConnection dbCntGuize;
string sqlstr;
string dbpvd;
string dbname;
dbpvd = "Provider=Microsoft.Jet.OLEDB.4.0";
dbname = "Data Source = " + ParentDir(Directory.GetCurrentDirectory(), 4) + "\\施肥数据库\\果类施肥.mdb";
dbCntGuize = new OleDbConnection(dbpvd + ";" + dbname);
dbCntGuize.Open(); //打开“施肥比例1”表
OleDbCommand dbcmd;
sqlstr = "select * from 施肥比例1";
dbcmd = new OleDbCommand(sqlstr, dbCntGuize);
OleDbDataReader myreader = dbcmd.ExecuteReader(); object N1 = 0;
N2 = 0;
N3 = 0;
while (myreader.Read())
{
N1 = myreader["N"];
N2 = myreader["N"];
N3 = myreader["N"];
}
myreader.Close(); return N1; }
测试过了 没错!!!!