Datastage Lookup

By using lookup we join the data from more than one table, we can implement the same using join stage, then what is the need of Lookup stage especially in Datastage?

Questions by nagarjuna900   answers by nagarjuna900

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Datastage lookup has some additional benefits over join stage :

a) A lookup stage supports reject link which is not supported by join stage.
b) Lookup stage has an option to fail the job if the lookup fails.This is especially useful when the lookup is always expected to be sucessful.
c)Lookup stage keeps the reference data into memory which yields better result for small volume of data.
d)Lookup stage does not require the data to be sorted.For join stage the sorted data is required.
e)In lookup stage,the columns with different column names can be joined as well.For join stage,the column names must be similar.

Because of above characteristics,lookup stage is used in Datastage and is more popular.

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