Supply input values for an unconnected Lookup transformation from a :LKP expression in another transformation. The arguments are local input ports that match the Lookup transformation input ports used in the lookup condition. Use the following syntax for a :LKP expression:
argument, argument, ...
To continue the example about the retail store, when you write the update strategy expression, the order of ports in the expression must match the order in the lookup condition. In this case, the ITEM_ID condition is the first lookup condition, and therefore, it is the first argument in the update strategy expression.
IIF(ISNULL(:LKP.lkpITEMS_DIM(ITEM_ID, PRICE)), DD_UPDATE, DD_REJECT)
Use the following guidelines to write an expression that calls an unconnected Lookup transformation:
The order in which you list each argument must match the order of the lookup conditions in the Lookup transformation.
The datatypes for the ports in the expression must match the datatypes for the input ports in the Lookup transformation. The Designer does not validate the expression if the datatypes do not match.
If one port in the lookup condition is not a lookup/output port, the Designer does not validate the expression.
The argument ports in the expression must be in the same order as the input ports in the lookup condition.
If you use incorrect :LKP syntax, the Designer marks the mapping invalid.
If you call a connected Lookup transformation in a :LKP expression, the Designer marks the mapping invalid.
Avoid syntax errors when you enter expressions by using the point-and-click method to select functions and ports.