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
4,286 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
1,060 reads
2016-11-15
1,313 reads
2016-05-31
1,593 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)
926 reads
2012-03-08
2,811 reads
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Question of the Day
Specifying the Collation
I am dealing with issues on my SQL Server 2022 instance related to collation. I have an instance collation of Latin1_General_CS_AS_KS_WS, but a database collation of Latin1_General_CI_AS. I want to force a few queries to run with a specified collation by using code like this:
DECLARE @c VARCHAR(20) = 'Latin1_General_CI_AS'
SELECT p.PersonType,
p.Title,
p.LastName,
c.CustomerID,
c.AccountNumber
FROM Person.Person AS p
INNER JOIN Sales.Customer AS c
ON c.PersonID = p.BusinessEntityID
COLLATE @c
Will this solve my problem? See possible answers