SQL 查询未返回正确的计数
我正在尝试计算行数并传递该计数值来执行一些逻辑。下面是代码：
static public int GetNoImagesofMakeID(int makeID)
{
string sql = "Select COUNT(*) from makeImages";
SqlDataAdapter da = new SqlDataAdapter(sql, ConnectionString);
DataTable dt = new DataTable();
da.Fill(dt);
return Convert.ToInt32(dt.Rows.Count);
}
protected void hideUnhideFileUpload(int makeID)
{
int count = caravans.GetNoImagesofMakeID(makeID);
if (count >= 10)
{
FileUpload2.Enabled = false;
}
else
{
FileUpload2.Enabled = true;
}
}
我不知道为什么计数总是 1。我在 SQL Server 上检查了相同的查询，它工作正常。但是，这里 dt.rows.count 总是返回 1。
任何帮助将不胜感激。谢谢。
I am trying to count the number of rows and pass that count value to do some logic. Below is the code:
static public int GetNoImagesofMakeID(int makeID)
{
string sql = "Select COUNT(*) from makeImages";
SqlDataAdapter da = new SqlDataAdapter(sql, ConnectionString);
DataTable dt = new DataTable();
da.Fill(dt);
return Convert.ToInt32(dt.Rows.Count);
}
protected void hideUnhideFileUpload(int makeID)
{
int count = caravans.GetNoImagesofMakeID(makeID);
if (count >= 10)
{
FileUpload2.Enabled = false;
}
else
{
FileUpload2.Enabled = true;
}
}
I don't know for what reason the count is always 1. I checked the same query on SQL Server and it's working fine. But, here dt.rows.count always return 1.
Any help will be highly appreciated. Thanks.
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该代码返回行数而不是 COUNT(*) 的结果。该 SQL 语句将始终只返回一行。您无需填充数据适配器，只需运行以下命令即可：
The code is returning the number of rows rather than the result of the COUNT(*). That SQL statement will always just return a single row. Rather than filling a data adapter, you can just run the command:
您的查询返回具有一个值（行数）的一行，因此 dt.Rows.Count 正确返回 1（意味着您的查询返回 1 行）。
使用数据表，您可以在
dt.Rows[0][0]（数据表的第 0 行第 0 列）处找到查询返回的计数Your query is returning one row with one value (the count of rows), so
dt.Rows.Countis correctly returning 1 (meaning 1 row returned by your query).Using a datatable, you would find the count returned by your query at
dt.Rows[0][0](row 0 column 0 of your datatable)count() 始终返回一行，无论其计数有多少行。 count() 是一个标量值。您需要做的是读取记录集中返回的值。
有关此问题中计数的更多信息： SQL Return code from Select count(* ）
A count() always returns a row, regardless of how many rows it is counting. a count() is a scalar value. What you need to do is read the value returned in the recordset.
More information about counts in this question: SQL Return code from Select count(*)
为什么您要获取表行数，而不是计数查询的返回值，因为这只会返回单行？
Why are you getting the table row count, instead of the returned value from your count query, as this will return only single row?