SqlCommand.ExecuteScalar Method
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.
Assembly: System.Data (in System.Data.dll)
Return Value
Type: System.ObjectThe first column of the first row in the result set, or a null reference (Nothing in Visual Basic) if the result set is empty. Returns a maximum of 2033 characters.
Implements
IDbCommand.ExecuteScalar()| Exception | Condition |
|---|---|
| SqlException |
An exception occurred while executing the command against a locked row. This exception is not generated when you are using Microsoft .NET Framework version 1.0. |
Use the ExecuteScalar method to retrieve a single value (for example, an aggregate value) from a database. This requires less code than using the ExecuteReader method, and then performing the operations that you need to generate the single value using the data returned by a SqlDataReader.
A typical ExecuteScalar query can be formatted as in the following C# example:
cmd.CommandText = "SELECT COUNT(*) FROM dbo.region"; Int32 count = (Int32) cmd.ExecuteScalar();
The following example creates a SqlCommand and then executes it using ExecuteScalar. The example is passed a string representing a new value to be inserted into a table, and a string to use to connect to the data source. The function returns the new Identity column value if a new row was inserted, 0 on failure.
static public int AddProductCategory(string newName, string connString) { Int32 newProdID = 0; string sql = "INSERT INTO Production.ProductCategory (Name) VALUES (@Name); " + "SELECT CAST(scope_identity() AS int)"; using (SqlConnection conn = new SqlConnection(connString)) { SqlCommand cmd = new SqlCommand(sql, conn); cmd.Parameters.Add("@Name", SqlDbType.VarChar); cmd.Parameters["@name"].Value = newName; try { conn.Open(); newProdID = (Int32)cmd.ExecuteScalar(); } catch (Exception ex) { Console.WriteLine(ex.Message); } } return (int)newProdID; }
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
// cast will generate an error when result is null
newProdID = (Int32)cmd.ExecuteScalar();
// if you test like the following code you run the query twice
// which might be best to avoid for performance reasons
if (cmd.ExecuteScalar() == null)
{
newProdID = 0;
}
else
{
newProdID = (Int32)cmd.ExecuteScalar();
}
//Store result in an object avoids running the query twice then just test object
Object scalarObj = null;
scalarObj = cmd.ExecuteScalar();
if (scalarObj != null)
newProdID = (Int32)scalarObj;
- 8/2/2009
- Gregory Kornblum
