what is the main differences between Lookup, Join and Merge
stages?
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Answer Posted / jana520
all are used to join tables , but
lookup: when the reference data is very less we use lookup.
bcoz the data is stored in buffer. if the reference data is
very large then it wl take time to load and for lookup.
join: if the reference data is very large then we wl go for
join. bcoz it access the data directly from the disk. so the
processing time wl be less when compared to lookup. but here
in join we cant capture the rejected data. so we go for merge.
merge: if we want to capture rejected data(when the join key
is not matched) we use merge stage. for every detailed link
there is a reject link to capture rejected data.
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