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
4,362 reads
UNION
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
2018-06-12
1,065 reads
2016-11-15
1,317 reads
2016-05-31
1,596 reads
Union Forcing Distinct
The use of union would seem to force a distinct in each of the select statements being unioned. The use multiple unions, with mixed union and union all clauses, seems to cause haphazard results.
2013-05-14 (first published: 2013-04-30)
932 reads
2012-03-08
2,817 reads
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Question of the Day
Identities and Sequences III
When thinking of the Identity property for auto incrementing columns and sequences for the same action, which can be used with the BIGINT data type?
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