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Denodo Disparat sources join without Cache.

Hi Guys, I am new to Denodo. I have installed Express edition on my laptop and running a sample task. I have two disparate data sources (Postgres and MySQL), Postgres has agents table while MySQL has Customer and Orders data. When I execute a join statement between agents and Customer data it return 0 rows, until I cache Customer data. Is there any way we can execute join statement between different sources without Caching, as It results replication cost? both Virtual Plans (_PG Source_ , _MYSQL Source_ ) return some rows but Inner Join Plan results 0 rows.
join Cache
user
18-12-2019 06:42:55 -0500
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3 Answers

Hi, Denodo does support joins between disparate data sources without requiring the use of the cache; it can also push down joins into the data sources if the data source supports the operation. I would ensure that either the cache is disabled if you don’t want to use it or that each view has been preloaded into the cache. If [full caching](https://community.denodo.com/docs/html/browse/latest/vdp/administration/cache_module/cache_modes/full_mode) is enabled on a view, the data source itself will never be queried for the data—only the cache. I use the Execution Trace tab in the Query Results window to check if Denodo is utilizing the cache while running a query; cache nodes will show up in grey. You can find more information about caching in Denodo on the [Configuring the Cache](https://community.denodo.com/docs/html/browse/7.0/vdp/administration/server_administration_-_configuring_the_server/configuring_the_cache/configuring_the_cache) page of the Denodo Community. Hope this helps!
Denodo Team
19-12-2019 07:02:31 -0500
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I just changed a scenerio and It worked actualy, It wasn't working for Text field, i.e. If the join columns are text. (I really don't know why) but it just worked on Number columns. However, when I checked the hashes of same values, different sources, it gave me different results. I can't attach the images here. (or I don't know the pattern to attach) Can you please check?
user
19-12-2019 09:34:20 -0500
Hi, For a join to work, the hash should be the same for entries from both sources. In the case of a text field, this means that the capitalization as well as leading and trailing spaces must be the same on both strings. For more information about handling differences between strings in Denodo I suggest looking at this similar [Denodo Community Q&A](https://community.denodo.com/answers/question/details?questionId=9060g000000TQqeAAG&title=Different+Hashes+for+same+values+hash%28%29) question. Hope this helps!
Denodo Team
26-12-2019 14:12:56 -0500
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