从SQL检索的ExecuteScalar值（） [英] Retrieving value from sql ExecuteScalar()

问题描述

我有以下内容：

String sql = "SELECT * FROM Temp WHERE Temp.collection  = '" + Program.collection + "'";
SqlConnection conn = new SqlConnection(connString);
SqlCommand cmd = new SqlCommand(sql, conn);
Program.defaultCollection = (String)cmd.ExecuteScalar();

和我要执行该语句后拿到的第二列。我知道这将返回只有一排有两列

And I want to get the second column after executing the statement. I know it will return only one row with two columns

我看了网上说我将不得不读取结果中的每一行，还有没有别的办法？

I have read online that I will have to read each row of the result, is there any other way?

推荐答案

的ExecuteScalar 会从结果集的第一行的第一列。如果你需要访问不止这些，你就需要采取不同的方法。像这样的：

ExecuteScalar gets the first column from the first row of the result set. If you need access to more than that you'll need to take a different approach. Like this:

DataTable dt = new DataTable();
SqlDataAdapater sda = new SqlDataAdapter(sql, conn);
sda.Fill(dt);

Program.defaultCollection = dt.Rows[0]["defaultCollection"];

现在，我才知道的字段名称可能不是 defaultCollection ，但你可以填写在

Now, I realize that the field name may not be defaultCollection, but you can fill that in.

从的为的ExecuteScalar MSDN文档：

From the MSDN documentation for ExecuteScalar:

执行查询，并在由该查询返回的结果集返回第一行的第一列。其他列或行被忽略。

Executes the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.

现在，作为建议的最后一点，请包装在所有的ADO.NET对象使用语句。像这样的：

Now, as a final bit of advice, please wrap all ADO.NET objects in a using statement. Like this:

using (SqlConnection conn = new SqlConnection(connString))
using (SqlDataAdapter sda = new SqlDataAdapter(sql, conn))
{
   DataTable dt = new DataTable();
   sda.Fill(dt);

   // do something with `dt`
}

这将确保他们得到妥善处置。

this will ensure they are properly disposed.

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