We have a project that is taking data from a database, and ultimately pushing to Tableau. There are date fields that appear as dates in Paxata, but when sent to Tableau are null. Changing them into text in Paxata, then back to date in Tableau solved it, but wondering if there is another way?
It's possible that column with date values in it has mixed data types meaning most of the values are dates but some of them could be characters as well. You may want to bring up filtergram on this column and inspect if it has any invalid contents (you will see proportionate red bar at the bottom of the filtergram). I would explicitly convert to column to date type before publishing and pushing it out to Tableau. Also its a good idea to make sure that date format of the column is consistent - meaning you don't have date with - and / as separators.
Please let me know if this helps. Otherwise I can setup a call and resolve the issue.