I am by no means a SQL expert, but try changing the last bit to WHERE b.field1='TRUE' instead of AND b.field1 IS TRUE
Benjamin, if I did that I'd be excluding the results from TableA that I wanted. I'd be getting something like below as 3, 4, and 5 don't have anything in Table B so it doesn't meet the requirements of the filter. To your point, there is another way to accomplish this by adding an OR b.field1 IS NULL. I haven't been able to figure out OR statements either.
FROM table_a a
from table_b b
where b.field1 = 'TRUE'
on b_table.id = a.id
I think I need to edit my initial question to clarify. I could do it as a custom sql query, I'm trying to do the Joins within Tableau as opposed to doing a custom SQL query. I've had to do the custom sql queries to pull the data into tableau for every dataset I've pulled in because of CTEs, casting, and other things where I couldn't figure out how to do it in Tableau.
Having said that, Alex, that does appear like it would work. Unfortunately I'd call it another way to ask the question, not the type of answer I was looking for.
Many thanks! That appears to be exactly what I was looking for. I'll have to play with it a bit but at least know where to look now! I had a feeling it was a simple one as it seems like it would be a pretty common problem.