Combining multiple subject areas but using one as the main data set

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Hi All,

As there are certain subject areas only that would contain information needed but also have it's own limitations, I am trying to combine two subject area but using one of them as the main list.

I've already tried linking two subject areas using union, also tried it as union all but it still doesn't use the subject area that i want to use as the main source for number wise.

In summary below are the two subject areas that I want to combine:

1. "Workforce Management - Worker Assignment Real Time" - I want to use this one as my main/list source