I guess this one is self-confessing:

alter table [Order]

add

DateTimeOrdered as dbo.JsonDateTime([Json], 'DateTimeOrdered', 'yyyy-MM-dd HH:mm:ss') persisted

go

create index IX_Order_DateTimeOrdered on [Order](DateTimeOrdered)

What to add?

Probably only this:

Extract all the other values from b..y JSON (XML, whatever), store them in proper tables and use all the advantages of relational databases!