# Lookup Join

**URL:** <https://forum.cloverdx.com/t/lookup-join/195>\
**Category:** CloverDX Platform\
**Created:** [July 27, 2007, 12:00am UTC](https://forum.cloverdx.com/t/lookup-join/195 "2007-07-27T00:00:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![vsvobodatrask.cz](https://avatars.discourse-cdn.com/v4/letter/v/dfb087/32.png) [@vsvobodatrask.cz](https://forum.cloverdx.com/u/vsvobodatrask.cz)\
**Post date:** [July 27, 2007, 12:00am UTC](https://forum.cloverdx.com/t/lookup-join/195/1 "2007-07-27T00:00:00Z")

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Hi,

Can you tell me how work the component Lookup Join.

I think, that the component Lookup Join work as merge or can I this component use different with merge records from database.

Thanks

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**Author:** ![dpavlis](https://avatars.discourse-cdn.com/v4/letter/d/90ced4/32.png) [@dpavlis](https://forum.cloverdx.com/u/dpavlis)\
**Post date:** [July 27, 2007, 8:41pm UTC](https://forum.cloverdx.com/t/lookup-join/195/2 "2007-07-27T20:41:58Z")

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The LookupJoin works similarly to HashJoin - it uses pre-defined lookup table and joins all input records with records in the lookup table.

The advantage is that you may define internally lookup table - SimpleLookup/DBLookup/RangeLookup, populate it somehow in graph (using LookupReaderWriter) and then (in following phase) perform joining.