Now, we'll spend some time cleaning up the data that came from both input sources. With the Clean 3 step selected, use the Profile pane to examine the data and continue our flow. The first two fields indicate some issues that need to be addressed:
The Table Names field was generated by Tableau Prep as part of Union 1 to indicate the source of the records. The Airline field came only from the Excel files (you can confirm this by selecting it in the profile pane and observing the highlighted path of the field in the flow pane). Click the null value for Airline and observe the brushing: this is proof that the NULL values ...
