Why don't you write Custom SQL for those two sources and make an extract ?
Hi Hrvoje, thanks for the response
So i now have 4 identical extracts in my workbook. I want to combine them with 'UNION ALL'. I have limitations doing this on my database server so cant do a custom SQL to my database. Is there a way to create a new extract on the 4 i already have?
You can append extracts that have the same schemas. Works similarly to UNION, but is a big pain.
Sometimes you can get the effect of a UNION by using a "scaffold" source that has the right dimensions (and nothing else) that becomes the primary source and then blend in the additional sources. If you're doing multiple extracts because the DB can't handle the load then your volumes are likely to be too large for a Tableau data blend, those top out at around 100K linking values in my own use (beyond that and the view refresh times start getting too slow). So the only option I can think of at this time is what Thomas wrote.
At the Tableau Conference last month they demoed UNION'ing multiple data sources, so I'd expect to see that as a new feature sometime in 2016.
Having tons of data for tableau to visualize is always a bad idea. Human
eyes can only see so much at a time. It is further aggravated in the era of
ADD/ADHD with short attention span.
In case of large volume of data, it's preferred to pre-aggregate them in
database and create a view with only the necessary data for visualization.
On Tue, Nov 10, 2015 at 6:35 AM, Jonathan Drummey <
I think you and I are talking about different things. The number of marks in the view (from your post) and the number of linking values aka "cardinality of the blend" aka number of blended values (from mine). I'm with you that 100K+ marks in a single view is likely to be non-useful, though I have seen views from Allan Walker (maps) and Richard Leeke (network traffic) that were drawing that many marks and had useful information being displayed.
What I was referencing was that in order to pull off a "scaffold + data blend for union" the number of distinct values of the linking dimension(s) may be so large that the time Tableau takes to do the blend as part of refreshing the view (no matter how many marks are actually displayed in the view) is too long for what is desired.
When replying via email, the forum always makes it look like addressing the
What I was trying to say is a general comment to the problem in this
Regarding the vizzies you mentioned, I wonder what are the minimum number
of marks to get the same insights? Can we subsample the dataset to get the
On Wednesday, November 11, 2015, Jonathan Drummey <