SELECT

  Sum(SALEITEMS.QUANTITY),

  Sum(SALEITEMS.QUANTITY * SALEITEMS.COSTPRICEEX)

FROM

  SALES SALES

  INNER JOIN SALEITEMS SALEITEMS ON SALES.LINECODE = SALEITEMS.LINECODE

WHERE

  SALES.POSTSTATUS = 'Posted' AND

  SALES.SALE_DATE BETWEEN :vStartDate AND :vEndDate AND

  SALEITEMS.SKU = :vSKU AND

  SALES.CASHCREDIT = 'Cash'

The first thing...

Are the indices statistics up to date ?

If so...

You could try this one:

SELECT

  Sum(SALEITEMS.QUANTITY),

  Sum(SALEITEMS.QUANTITY * SALEITEMS.COSTPRICEEX)

FROM

  SALES SALES

  INNER JOIN SALEITEMS SALEITEMS ON SALES.LINECODE = SALEITEMS.LINECODE

WHERE

  SALES.POSTSTATUS = 'Posted' AND

  SALES.SALE_DATE BETWEEN :vStartDate AND :vEndDate AND

  SALEITEMS.SKU+0 = :vSKU AND

  SALES.CASHCREDIT = 'Cash'


and see if it uses the Date index.

see you !