Understanding UNION and UNION ALL in SQL Server
A short look at the differences in UNION and UNION ALL in a SELECT query.
2025-04-07
4,355 reads
A short look at the differences in UNION and UNION ALL in a SELECT query.
2025-04-07
4,355 reads
Sometimes there is a need to combine data from multiple tables or views into one comprehensive dataset. This may be for like tables within the same database or maybe there is a need to combine like data across databases or even across servers. I have read about the UNION and UNION ALL commands, but how do these work and how do they differ?
2019-12-05
Paul White digs into row goals as he explains some interesting and inconsistent behavior with UNION ALL queries in SQL Server.
2017-06-13
5,896 reads
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I have a database, DNRTest, that has a number of tables and other objects in it. The other day, I was trying to mock up a test and ran this code on the same server:
-- run yesterday CREATE DATABASE DNRTest2 GO USE DNRTest2 GO CREATE TABLE NewTable (id INT) GOToday, I realize that I need a copy of DNRTest for another mockup, and I run this:
-- run today USE Master BACKUP DATABASE DNRTest TO DISK = 'dnrtest.bak' GO RESTORE DATABASE DNRTest2 FROM DISK = 'dnrtest.bak' WITH REPLACEWhat happens? See possible answers