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
4,375 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 Long is a Long I/O?
In SQL Server 2025, a long I/O is recorded in the error log with message 833. How long much an I/O request be outstanding before this message is written to the log?
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