Explain lookup vs join vs merge in datastage?
Join | Lookup | Merge |
---|---|---|
Used when joining large tables. | They are used while doing a range lookup within a small reference dataset. | Used when multiple updates and reject links are required within a dataset. |
The performance of Join is increased while key-sorting data based on input links. | It does not require data on the input or the reference link to be sorted out. | It can have any number of input links, but it has to be matched with the number of reject links. |
The key columns must be the same in the tables. | The Key column names do not have to be the same in the primary and lookup tables. | Here, to ensure minimum memory requirements, users have to ensure that rows having the same fundamental column values are located in the same portion and are divided by the same node. |
BY Best Interview Question ON 06 Jun 2020