如何获取存储过程的返回值

Question

Probably an easy-to-answer question. I have this procedure:

CREATE PROCEDURE [dbo].[AccountExists]
    @UserName nvarchar(16)
AS
IF EXISTS (SELECT Id FROM Account WHERE UserName=@UserName)
SELECT 1
ELSE SELECT 0 

When I have ADO.NET code that calls this procedure and does this:

return Convert.ToBoolean(sproc.ExecuteScalar());

Either true or false is returned.

When I change the stored procedure to RETURN 1 or 0 instead of SELECT:

ALTER PROCEDURE [dbo].[AccountExists]
    @UserName nvarchar(16)
AS
IF EXISTS (SELECT Id FROM Account WHERE UserName=@UserName)
RETURN 1
ELSE RETURN 0 

sproc.ExecuteScalar() returns null. If I try sproc.ExecuteNonQuery() instead, -1 is returned.

How do I get the result of a stored procedure with a RETURN in ADO.NET?

I need AccountExists to RETURN instead of SELECT so I can have another stored procedure call it:

--another procedure to insert or update account

DECLARE @exists bit

EXEC @exists = [dbo].[AccountExists] @UserName 

IF @exists=1
--update account
ELSE
 --insert acocunt

Answer 1

Add a parameter, using ParameterDirection.ReturnValue . The return value will be present in the paramter after the execution.

Answer 2

Also, to retrieve the result (or any other output parameter for that matter) from ADO.NET you have to loop through all returned result sets first (or skip them with NextResult)

This means that if you have a procedure defined like this:

CREATE PROC Test(@x INT OUT) AS
    SELECT * From TestTable
    SELECT @x = 1

And try to do this:

SqlCommand cmd = connection.CreateCommand();
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "Test"
cmd.Parameters.Add("@x", SqlDbType.Int).Direction = ParameterDirection.Output;
cmd.Parameters.Add("@retval", SqlDbType.Int).Direction = ParameterDirection.ReturnValue;

cmd.Execute();
int? x = cmd.Parameters["@x"].Value is DBNull ? null : (int?)cmd.Parameters["@x"].Value;

Then x will contain null. To make it work, you have to execute the procedure like:

using (var rdr = cmd.ExecuteReader()) {
    while (rdr.Read())
        MaybeDoSomething;
}
int? x = cmd.Parameters["@x"].Value is DBNull ? null : (int?)cmd.Parameters["@x"].Value;

In the latter case, x will contain 1 as expected.

Answer 3

ExecuteScalar returns the first column of the first row. Since you were no longer selecting, and creating a resultset, that is why it was returning null. Just as FYI. John Saunders has the correct answer.

Answer 4

I tried the other solutions with my setup and they did not work but I'm using VB6 & ADO 6.x. I also want to point out that a proc return of 0 indicates successful. Don't forget there are functions available too which don't have that convention. Found this on MSDN and it did work for me:

Debug.Print "starting at ..." & TimeValue(Now)

Dim cn As New ADODB.Connection
Dim cmd As New ADODB.Command
'These are two possible connection strings. You could also have Integrated Security instead of these for SqS for security
'cn.ConnectionString = "Data Source=[yourserver];User ID=[youruser];Password=[yourpw];Initial Catalog=[yourdb];Provider=SQLNCLI10.1;Application Name=[yourapp]"
cn.ConnectionString = "Data Source=[yours];User ID=[youruser];Password=[yourpassword];Initial Catalog=[Yourdb];Provider=sqloledb;Application Name=[yourapp]"
cn.Open

cmd.ActiveConnection = cn
cmd.CommandText = "AccountExists"
cmd.CommandType = adCmdStoredProc
cmd.Parameters.Append cmd.CreateParameter(, adInteger, adParamReturnValue)
cmd.Parameters.Append cmd.CreateParameter("UserName",adVarChar, adParamInput, 16, UserNameInVB)

cmd.Execute
Debug.Print "Returnval: " & cmd.Parameters(0)
cn.Close

Set cmd = Nothing
Set cn = Nothing

Debug.Print "finished at ..." & TimeValue(Now)

The results will appear in the immediate window when running this (Debug.Print)

Answer 5

Several ways are possible to get values back using VBA:

1. Recordset
2. Count of records affected (only for Insert/Update/Delete otherwise -1)
3. Output parameter
4. Return value

My code demonstrates all four. Here is a stored procedure that returns a value:

Create PROCEDURE CheckExpedite
    @InputX  varchar(10),
    @InputY int,
    @HasExpedite int out
AS
BEGIN
    Select @HasExpedite = 9 from <Table>
    where Column2 = @InputX and Column3 = @InputY

    If @HasExpedite = 9
        Return 2
    Else
        Return 3
End

Here is the sub I use in Excel VBA. You'll need reference to Microsoft ActiveX Data Objects 2.8 Library.

Sub CheckValue()

    Dim InputX As String: InputX = "6000"
    Dim InputY As Integer: InputY = 2014

    'open connnection
    Dim ACon As New Connection
    ACon.Open ("Provider=SQLOLEDB;Data Source=<SqlServer>;" & _
        "Initial Catalog=<Table>;Integrated Security=SSPI")

    'set command
    Dim ACmd As New Command
    Set ACmd.ActiveConnection = ACon
    ACmd.CommandText = "CheckExpedite"
    ACmd.CommandType = adCmdStoredProc

    'Return value must be first parameter else you'll get error from too many parameters
    'Procedure or function "Name" has too many arguments specified.
    ACmd.Parameters.Append ACmd.CreateParameter("ReturnValue", adInteger, adParamReturnValue)
    ACmd.Parameters.Append ACmd.CreateParameter("InputX", adVarChar, adParamInput, 10, InputX)
    ACmd.Parameters.Append ACmd.CreateParameter("InputY", adInteger, adParamInput, 6, InputY)
    ACmd.Parameters.Append ACmd.CreateParameter("HasExpedite", adInteger, adParamOutput)

    Dim RS As Recordset
    Dim RecordsAffected As Long

    'execute query that returns value
    Call ACmd.Execute(RecordsAffected:=RecordsAffected, Options:=adExecuteNoRecords)

    'execute query that returns recordset
    'Set RS = ACmd.Execute(RecordsAffected:=RecordsAffected)

    'get records affected, return value and output parameter
    Debug.Print "Records affected: " & RecordsAffected
    Debug.Print "Return value: " & ACmd.Parameters("ReturnValue")
    Debug.Print "Output param: " & ACmd.Parameters("HasExpedite")

    'use record set here
    '...

    'close
    If Not RS Is Nothing Then RS.Close
    ACon.Close

End Sub

Answer 6

Just some advice, but by default, a Stored Procedure returns 0 unless you specify something else. For this reason, 0 is often used to designate success and non-zero values are used to specify return error conditions. I would go with John's suggestion , or use an output parameter

Answer 7

If you are planing on using it like the example below AccountExists might be better off as a function.

Otherwise you should still be able to get the result of the stored procedure by calling it from another one by doing a select on the result.