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
4,079 reads
UNION ALL
UNION vs. UNION ALL in SQL Server
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
UNION ALL Optimization
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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Question of the Day
How Many Can Be the Greatest
I am trying to analyze a number of columns in a large table to determine the highest value for each row. In SQL Server 2022, we have the GREATEST function, which will return the greatest value from those columns passed in. How many columns can I include in an expression like this:
select GREATEST( col1, col2, col3, ...)See possible answers