Is it possible to access fields across derived tables?
SELECT *
FROM (SELECT ID, COL1A FROM Table1) T1
JOIN (SELECT ID, COL2A FROM Table2) T2
ON T1.ID = T2.ID
JOIN (SELECT ID, (COL3A + T2.COL2A) AS SUM FROM Table3) T3
ON T1.ID = T3.ID
You would put the expressions using multiple columns in the
SELECT
clause:There is no need for derived tables at all.