Need SQL query to update the column using case when by joining two tables in Netezza Database

There are 2 tables : Sales & Transaction. I need to update the INDICATOR column of the Sales table using CASE WHEN by joining these two tables in Netezza database.

Using below query but not working. Error - Update canceled: attempt to update a target row with values from multiple join rows

Update Sales s 
SET indicator = 
 CASE  
     WHEN  t.retail >= s.PRICe then 'Y'
     WHEN  t.retail <  s.PRICE then 'N'
     ELSE NULL END
FROM TRANSACTION t
     WHERE s.id = t.id and s.STORE_ID = t.store_id;