Better to have Yes no field as integer or string 1 character?

[TinyTimothy2]

Is it better to have Yes no field as integer or string 1 character Y, N
Is there really a performance and space diff for 1 B row table?
I am thinking of switching back Y/N because it is better and more intuitive in visuals and filters.

[otykier]

All that matters is the cardinality of the column. So in theory, there should be no difference between using 0/1 (integer), true/false (boolean) or "Y"/"N" (one character string) or even "Yes"/"No" (multiple character string). Use the option that makes most sense for your model consumers.

[TinyTimothy2]

Does the size matter? Won't characters take up more space which would also take up more memory?

[otykier]

Doesn’t matter. String columns are dictionary encoded.

If you’re curious about this stuff, please spend some time educating yourself on the VertiPaq Engine, which is the storage engine behind Power BI semantic models and Analysis Services tabular models.