Getting a distinct value across 2 union sql server tables
I'm trying to get all distinct values across 2 tables using a union. The idea is to get a count of all unique values in the columnA column without repeats so that I can get a summation of all columns that contain a unique columnA. This is what I tried (sql server express 2008) select count(Distinct ColumnA) from ( select Distinct ColumnA as ColumnA from tableX where x = y union select Distinct ColumnA as ColumnA from tableY where y=z ) SELECT COUNT(distinct tmp.ColumnA) FROM ( (SELECT ColumnA FROM TableX WHERE x=y) UNION (SELECT ColumnA FROM TableY WHERE y=z) ) as tmp The extra distincts on