Knowledge Drop
Last Tested: Aug 13, 2018
For unpivoted queries, there is no limit. You could potentially at any time build a result set that is wide enough to crash a browser if unpivoted. (The benchmark there is around 30,000 data cells.)
We do apply a default of 50 columns (docs) and a hard limit of 200 columns when pivoting in order to try to control the amount of data. (Note that "column limit" here is a bit of a misnomer—the limit is actually 200 pivoted values. So if you have 2 measures selected, you can have up to 2 measures x 200 pivoted values = 400 columns. But this many columns could crash your browser.)
If you need more than that, download the results unpivoted and then pivot in an external tool like Excel instead.
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