After you configure the ports, define a lookup condition to compare transformation input values with values in the lookup source or cache. To increase performance, add conditions with an equal sign first.
In this case, add the following lookup condition:
ITEM_ID = IN_ITEM_ID
PRICE <= IN_PRICE
If the item exists in the mapping source and lookup source and the mapping source price is less than or equal to the lookup price, the condition is true and the lookup returns the values designated by the Return port. If the lookup condition is false, the lookup returns NULL. When you write the update strategy expression, use ISNULL nested in an IIF function to test for null values.