IMPORTANT:
- Clause must appear in a certain order
- from clause and select. . . group clause two parts is necessary
- Other clauses are optional
- In the LINQ query expression, select the expression clause in the final.
- As many from the can. . . let. . . where clause
from the clause must
from. . . let. . . The optional where clause
orderby clause is optional
select. . . The group clause must
Follow-up inquiries into the optional part