如果查询返回任何行数, C# SQL
原标题：C# SQL if query returns any rows count
What is the simplest and most efficient way to find if a data returns using a query? I m using DataTable like sqlAdapter.Fill(_table1) and then doing _table1.Rows.Count to see if a datatable has any rows. Is there any classes and functions in C# that just gives me if there are any rows. I don t need the data of the rows. Just the count is what I need. I m running this query against very large datasets so I don t wanna fill the datatable with all the row info.
最佳回答
string myScalarQuery = "select count(*) from TableName";
SqlCommand myCommand = new SqlCommand(myScalarQuery, myConnection);
myCommand.Connection.Open();
int count = (int) myCommand.ExecuteScalar();
myConnection.Close();
Possible optimization of the query per the comments bellow: Select Top 1 * FROM TableName
问题回答
The least expensive way is using SqlDataReader s HasRows property
UPDATE: of course, the most efficient SELECT query will be like "Select Top 1 1 FROM TableName", which doesn t even need to pull any column data.
using (SqlConnection conn = new SqlConnection(connectionString))
{
conn.Open();
using (SqlDataReader rdr = cmd.ExecuteReader())
{
if (rdr.HasRows)
...
}
}
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