what is the main differences between Lookup, Join and Merge
stages?
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Answer Posted / kpk
all three stages are used to join database tables based on a
key column.
Lookupsate: input 1 reference any number (if oracle or DB2
only 1 reference link) one out put link and one reject link.
faster if the volume of data is less than the memory size.
if the siz is too huge then DS uses scrap files to store the
remaining datas and that hinders the performance.
Joinstage: can have any (but i think only 16 )tables can be
joined. does not use memory, look up is done on table level,
so would be better to use if the data volume is pretty
huge.dosent have any reject link. only one out put link.
Mergestage: can have any number of input link and update
link. need to have a key column. can have any number of
reject link. only one out put link.
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