# ExtMergeJoin won't handle left outer join

**URL:** <https://forum.cloverdx.com/t/extmergejoin-wont-handle-left-outer-join/115>\
**Category:** CloverDX Platform\
**Created:** [July 16, 2007, 12:00am UTC](https://forum.cloverdx.com/t/extmergejoin-wont-handle-left-outer-join/115 "2007-07-16T00:00:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![oldforum](https://avatars.discourse-cdn.com/v4/letter/o/13edae/32.png) [@oldforum](https://forum.cloverdx.com/u/oldforum)\
**Post date:** [July 16, 2007, 12:00am UTC](https://forum.cloverdx.com/t/extmergejoin-wont-handle-left-outer-join/115/1 "2007-07-16T00:00:00Z")

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Hi,

I can’t seem to make Ext\_Merge\_Join component hanlde ‘left outer join’ nor ‘allow slave duplicates’ options. When using either of these options, the component won’t output the expected data.

Especially, if join key has a null value on some rows, this will block the component.

Ext Hash Join works just fine, but is much slower when volume grow in size…

Is this a known problem, or am I missing something ?

Franck

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<div class="post-metadata">

**Author:** ![oldforum](https://avatars.discourse-cdn.com/v4/letter/o/13edae/32.png) [@oldforum](https://forum.cloverdx.com/u/oldforum)\
**Post date:** [July 16, 2007, 8:23am UTC](https://forum.cloverdx.com/t/extmergejoin-wont-handle-left-outer-join/115/2 "2007-07-16T08:23:44Z")

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Hi, I tried to recreate your problem but everything works correctly: there is no error message and data are joined properly. Can you send more info about the problem (graph and data probe)?  
With regards  
Agata Vackova