Normal Lookup:In this when ever ds wants to look up it just place the target table data into buffer.
Sparse Lookup:To look up itr fires an sql query to the database instead of placing into buffer.To use sparse look up your target database must be larger than source table and your target should be a database of any type.
normal look-up: all the reference table data is stored in the buffer for cross- check with the primary table data. sparse lookup: each record of the primary table is cross checked with the reference table date
the types of look-ups will araise only if the reference table is in database. so depending on the size of the reference table we will set the type of lookup to implement.
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