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
4,435 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
The Range of Customers
I have this data in the OrderHeader table in a SQL Server 2025 database (ordered by CustomerID ASC):
orderid orderdate customerid complete 3 2025-05-10 00:00:00.0002 1 21 2024-01-10 00:00:00.0003 1 15 2023-10-28 00:00:00.0004 1 13 2025-03-08 00:00:00.0006 1 11 2024-04-02 00:00:00.0007 1If I run this query, how many rows are returned?
SELECT * from dbo.OrderHeader where customerid between 3 and '6'See possible answers