Maximum conditions in Switch statement in Tableau-Excel connection

I am working on a SQL in Tableau Desktop for extracting data from an Excel spreadsheet.

I have 125 subject codes to be categorized in 24 different departments.

I am using "Switch" statement for the same. The query works perfectly fine if I enter 13 different cases, however, it gives me below error when I try to input more than 13 cases.

Database error 0x80040E14: Expression too complex in query expression 'Switch([Subjectcode] in ("21:003"),"AF",[Subjectcode] in ("21:080","21:082","21:089","26:561"),"ACM",[Subjectcode] in ("21:014"),"AAAF",[Subjectcode] in ('.

Is there a limit for the number of cases that can be input to the Switch statement?

Please Note: I cannot use "IF..ELSE" statements as the Microsoft Jet Engine doesn't allow me to do the same in Tableau.