The Data Design preview function, more specifically the Merge Preview function, is borderline useless. Maybe 1 out of 20 times will the preview actually generate anything. Is it because the merge has 0 results? Is it because I merged on the wrong fields? Maybe I have the wrong join and it should be left instead of right?
Impossible to know without fully running the data design, and if you’re working through multiple joins within a design you have to join a potentially non-functioning merge into the full data set - whereas if the preview actually functioned as expected I could adjust as needed without having to complete the design. When working with large data sets, it’s extremely time consuming to always have to run a DD for each Merge to validate the output when the Preview feature should function.
I don’t remember having this issue so often in the past.
![](https://uploads-us-west-2.insided.com/gainsight-us/attachment/ff317cd7-4c3b-4a82-8baf-f6fb0b65af08.png)