Assuming a table level with columns level_id and level_name
I have a virtual table in my SQL Server 2016 query:
This is not a real query - I've simplified it as much as possible to illustrate the error
SELECT
    LEVEL .level_id,
    LEVEL .level_name
FROM
    LEVEL,
    ((SELECT
          LEVEL_ID AS lev_sum_level_id
      FROM
          LEVEL
      GROUP BY
          level_id) AS lev_sum
     JOIN
         (SELECT
              LEVEL_ID AS lev_det_level_id
          FROM
              LEVEL
          GROUP BY
              level_id) AS lev_det ON (lev_sum_level_id = lev_det_level_id)
  ) AS totals
The syntax error is on the line AS totals.
Msg 156, Level 15, State 1, Line 35
Incorrect syntax near the keyword 'AS'
Why is SQL Server not allowing this syntax? Seems fine if I simplify the virtual table query. Postgres allows it as-is
 
     
    