SQL Server : trigger handle multiple rows
<p>I have a trigger if I do multiple insert then I get an error on:</p>

<pre><code>IF((SELECT FACTREGELPRIJS FROM inserted) &gt; 0)
</code></pre>

<p>This is my trigger:  </p>

<pre><code>CREATE TRIGGER [dbo].[trg]
ON [dbo].[FACTUURREGEL]
AFTER INSERT
AS
BEGIN
    DECLARE @rowCount INT = @@ROWCOUNT 

    IF(@rowCount = 0)
        RETURN

    BEGIN TRY
        IF(EXISTS(SELECT 1 FROM inserted) 
           AND NOT EXISTS(SELECT 1 FROM deleted))
        BEGIN
            IF((SELECT FACTREGELPRIJS FROM inserted) &gt; 0)
            BEGIN
                RAISERROR('MAG geen prijs toegevoegd worden',16,1)
            END
            ELSE
            BEGIN
                UPDATE f 
                SET FACTREGELPRIJS = (p.PRODUCTPRIJS * f.FACTREGELHOEVEELHEID) - ((p.PRODUCTPRIJS * f.FACTREGELHOEVEELHEID)*(f.FACTREGELKORTING/100.0))
                FROM FACTUURREGEL f
                INNER JOIN PRODUCT p on p.PRODUCTID = f.PRODUCTID
            END
        END
    END TRY
    BEGIN CATCH
        ROLLBACK TRANSACTION;

        DECLARE
            @ErrorMessage   VARCHAR(400),
            @ErrorSeverity  INT,
            @ErrorState     INT

        SELECT
            @ErrorMessage   = ERROR_MESSAGE(),
            @ErrorSeverity  = ERROR_SEVERITY(),
            @ErrorState = ERROR_STATE()

        RAISERROR (@ErrorMessage , @ErrorSeverity, @ErrorState)
    END CATCH
END
</code></pre>

<p>How can I fix it? thank you</p>