Not sure what your exact use case is, I'm curious actually, but storing JSON strings should work much better. JSON functions are supported since SQL Server 2016 [0]. This is how I do it atm. I store only indexible content in table columns and everything else goes into an `attributes` JSON column. MSSQL supports indexes even on JSON fields, but I have not tried that, yet.
Secondly, JSON is already serialized, so it doesn't make sense to store as a base64 string. You're adding 30% data overhead to transform a string into a string. Base64 is useful for serializing opaque binary formats.
Lastly, some people might be getting a wry smile that you have the power of a relational database but are just trying to store "json" rather than an actual relational model.
You slap a full text index on the base64 string. There's only a finite number of base64 substrings for the un-encoded substrings "id", 42, etcetera, so you first filter on those. Then you decode those full strings into json and do the final filtering application side. Easy!
