How to write a query in sql with a calculated field?

Question

SQL

there is entity A { id:int, title:string, numplaces:int, freenumplaces:int }
there is entity B { id:int, product:int, tikets:int}
tables are not related
when querying select "id", "title", "numplaces", "freenumplaces" from A
freenumplaces should count as (select Sum(tikets) from B where product= A .id)

Answer 1

JOIN A with a selection from B pre-grouped by product

Answer 2

You can use INSERT INTO to first insert data into this column, and then just SELECT to get everything from the table.