Must specify table to select from ,statement 'blanked argeement (OOAT) could not be prepared

I receive this message (Must specify table to select from ,statement 'blanked argeement (OOAT) could not be prepared)

while execute this query from Query Manager. (SAP 8.82 pl 05)

DECLARE @DateFrom Date

DECLARE @DateTo Date

DECLARE @CardCode varchar(100)

SET @DateFrom = (select t20.StartDate FROM [ZAM_V_StartDate] T20 WHERE t20.StartDate <= '[%1]')  

SET @DateTo = (select t20.EndDate FROM [ZAM_V_EndDate] T20 WHERE t20.EndDate <= '[%2]') 

SET @CardCode =(SELECT t1.cardcode FROM ocrd T1 WHERE t1.cardcode <= '[%0]')

  SELECT Q1.*

  FROM (

  SELECT * FROM ZAM_F_SalesInvoice (@DateFrom, @DateTo)

  UNION ALL

  SELECT * FROM ZAM_F_SalesCredit (@DateFrom, @DateTo)

  )Q1

  where q1.cardcode = @CardCode

Note : t20.StartDate , t20.EndDate as Date

ZAM_V_EndDate : receive max docdate from oinv and orin

ZAM_V_StartDate : receive min docdate from oinv and orin

Please Advice