Of course, there is still the question of how to recreate rows from columnar storage. In 1999, Stephen Tarin patented the Tarin Transform Method, which uses a row reconstruction table to regenerate the rows. Mr. Tarin called columnar storage the Trans-Relational Model. This does not mean the model is beyond relational; this was more a marketing term, short for Transform Relational Model.
SQL Server documentation does not publish the row recreation algorithm it uses. I am presenting the Tarin's method here. It should still be good enough to give you a better understanding of the amount of work SQL Server has to do when it recreates rows from columns.
The following figure explains the Tarin Transform Method: ...
