Differences Between Connected and Unconnected Lookup:
connected
o Receives input values directly from the pipeline.
o uses Dynamic or static cache
o Returns multiple values
o supports user defined default values.
Unconnected
o Recieves input values from the result of LKP
expression in another transformation
o Use static cache only.
o Returns only one value.
o Doesn’t supports user-defined default values.
NOTES
o Common use of unconnected LKP is to update slowly
changing dimension tables.
o Lookup components are
(a) Lookup table. B) Ports c) Properties d) condition.
Lookup tables: This can be a single table, or you can
join multiple tables in the same Database using a Lookup
query override.You can improve Lookup initialization time
by adding an index to the Lookup table.
Lookup ports: There are 3 ports in connected LKP
transformation (I/P,O/P,LKP) and 4 ports unconnected LKP
(I/P,O/P,LKP and return ports).
o if you’ve certain that a mapping doesn’t use a
Lookup ,port ,you delete it from the transformation. This
reduces the amount of memory.
Lookup Properties: you can configure properties such as SQL
override .for the Lookup,the Lookup table name ,and tracing
level for the transformation.
Lookup condition: you can enter the conditions ,you want
the server to use to determine whether input data qualifies
values in the Lookup or cache .
when you configure a LKP condition for the transformation,
you compare transformation input values with values in the
Lookup table or cache ,which represented by LKP ports .when
you run session ,the server queries the LKP table or cache
for all incoming values based on the condition.
NOTE
- If you configure a LKP to use static cache ,you
can following operators =,>,<,>=,<=,!=.
but if you use an dynamic cache only =can be used .
- when you don’t configure the LKP for caching ,the
server queries the LKP table for each input row .the result
will be same, regardless of using cache
However using a Lookup cache can increase session
performance, by Lookup table, when the source table is
large.
Performance tips:
- Add an index to the columns used in a Lookup
condition.
- Place conditions with an equality opertor (=) first.
- Cache small Lookup tables .
- Don’t use an ORDER BY clause in SQL override.
- Call unconnected Lookups with :LKP reference
qualifier.
Hi,
I have one scenario.. i want to insert 4 times (Duplicate)
a row in the target. Please help me .
source row: abcabc
Tgt table:
abcabc
abcabc
abcabc
abcabc
Hi Friends,
I want lo truncate my records from target before loading
current month data,but i dont have permission to truncate
with truncate option
if u know any other way please give your valuable input for
this.
Thanks
Abhishek
I have scenario, i have 10 worklflows and i want run the
1st workflow first and immediately i want to run 10th
workflow has to run and am not bothering of 2 to 9
workflows? can any one help me how to do this? Thanks in
advance.....
along with your userid / name. ThanQ
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