The exact difference between Join,Merge and lookup is
The three stages differ mainly in the memory they use
DataStage doesn't know how large your data is, so cannot make an informed choice whether to combine data using a join stage or a lookup stage. Here's how to decide which to use:
if the reference datasets are big enough to cause trouble, use a join. A join does a high-speed sort on the driving and reference datasets. This can involve I/O if the data is big enough, but the I/O is all highly optimized and sequential. Once the sort is over the join processing is very fast and never involves paging or other I/O
Unlike Join stages and Lookup stages, the Merge stage allows you to specify several reject links as many as input links.
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RE: What is the exact difference betwwen Join,Merge an...
The exact difference between Join,Merge and lookup is
The three stages differ mainly in the memory they use
DataStage doesn't know how large your data is, so cannot make an informed choice whether to combine data using a join stage or a lookup stage. Here's how to decide which to use:
if the reference datasets are big enough to cause trouble, use a join. A join does a high-speed sort on the driving and reference datasets. This can involve I/O if the data is big enough, but the I/O is all highly optimized and sequential. Once the sort is over the join processing is very fast and never involves paging or other I/O
Unlike Join stages and Lookup stages, the Merge stage allows you to specify several reject links as many as input links.
RE: What is the exact difference betwwen Join,Merge an...
As of my knowledge join and merge both u used to join two files of same structure where lookup u mainly use it for to compare the prev data and the curr data.
RE: What is the exact difference betwwen Join,Merge and Lookup Stage??
join is uaed to connect maximum two tables or datasets, join does not have on reject link, merge can have more than two tables or datasets, merge have a reject link,merge have a master and update tables or datasets,
RE: What is the exact difference betwwen Join,Merge and Lookup Stage??
data selection is very easy in join dataselection is difficult in merge join does'nt support reject links merge support reject links join supports only 2 files or 2 databases merge supports no.of inputs so finally performance wise join is better than merge.
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