Make two queries and use IF, IERROR, ARRAYFORMULA and the array handling feature of Google Sheets.
It's not possible to get the desired result using a single QUERY because of the Google Query implementation. Fortunately the desired result could be obtained by using other Google Sheets features.
From the linked spreadsheet in the question
What I would like is a single query that would let me output all of the restaurants in a given neighborhood.
Then for each result, IF the restaurant matches a certain cuisine then display the cuisine. if it does not,
then leave the cell blank. Bonus points for sorting the output with desired cuisine on top, but that may be
asking too much and is really not important. So if I am in Strathcona and hungry, I can get a list of all
the places I've "been meaning to go to" in the area, and tonight I'm in the mood for Italian so:
I would like this output:
Poor Italian 1816 Howard St Italian
Lucy's 15 Main
Parallel 49 123908 Main
The following formula returns the desired output:
query('Sample Data'!A3:F10,"select A,C where B = 'Strathcona'"),
query('Sample Data'!A3:F10,"select D where B = 'Strathcona'")="Italian",
In order to make simple formula the neighbourhood and cuisine are "hardcoded" in the formula. In order to make the formula more easy of maintain, this values could be replaced by cell references but you should be aware that the query argument requires that strings be enclosed by using apostrophes.
Assume that A1 holds the value of the neighbourhood. In the formula, the "hardcoded" value
'Strathcona' could be replaced by
By the other hand, the case of the cuisine is out of the query argument, so it could be replaced by just the cell reference. Assume that B1 holds de the value of cuisine. In the formula, the "harcoded" value
"Italian" could be replaced by
Note to self