深入研究SQL SERVER 2005和多活动结果集（MARS）
SQL SERVER 2005引入了在单一连接上对多活动结果集（也称为MARS）或多个请求的支持。通过在与SQL SERVER 2005的连接上启用这一特性，当存在与Sqlconnection相关联的开放式SqlDataReader时，连接将不会中断。即使尚未关闭当前打开的SqlDataReader，也仍然能够在Sqlconnection上执行其他查询比如：SELECT，UPDATE，CREATETABLE等等。
举个简单的例子，就是在Northwind数据库里的订单表里取订单数据，而且把对应的子订单明细数据一起取出。
C#示例代码：<激光传真机>
string strSQL;
SqlConnectionStringBuilder ssb = new SqlConnectionStringBuilder();
ssb.DataSource = ".";
ssb.InitialCatalog = "Northwind";
ssb.UserID = "sa";
ssb.Password = "********";
ssb.MultipleActiveResultSets = true;
SqlConnection cn = new SqlConnection(ssb.ConnectionString);
SqlCommand cmdOrders, cmdDetials;
SqlParameter pCustID, pOrderID;
SqlDataReader rdrOrders, rdrDetials;
cn.Open();
strSQL = "SELECT OrderID,OrderDate from Orders WHERE CustomerID = @CustomerID";
cmdOrders = new SqlCommand(strSQL, cn);
pCustID = cmdOrders.Parameters.Add("@CustomerID", SqlDbType.NChar, 5);
strSQL = "SELECT ProductID,Quantity,UnitPrice from [ORDER dETAiLS] WHERE OrderID = @OrderID";
cmdDetials = new SqlCommand(strSQL, cn);
pOrderID = cmdDetials.Parameters.Add("@OrderID", SqlDbType.NChar, 5);
pCustID.Value = "ALFKI";
Console.WriteLine("Orders for {0}", pCustID.Value);
Console.WriteLine("=================");
rdrOrders = cmdOrders.ExecuteReader();
while (rdrOrders.Read())
{
Console.WriteLine("OrderID: {0} OrderDate:{1:d}", rdrOrders["OrderID"], rdrOrders["OrderDate"]);
pOrderID.Value = rdrOrders["OrderID"];
rdrDetials = cmdDetials.ExecuteReader();
while (rdrDetials.Read())
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2009-11-18 12:51:46
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insert into tb
values(1)
while @@ ......
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{
SqlConnection myConnection = new SqlConnection(myConnString);
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SqlTransaction m ......
declare @i int
set @i=1
while @i<30
begin
insert into test (userid) values(@i)
set @i=@i+1
end
---------------
while 条件
begin
执行操作
set @i=@i+1
end
WHILE
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group by convert(char(10),happentime ,120) order by date desc
s ......
