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
4,303 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
1,063 reads
2016-11-15
1,314 reads
2016-05-31
1,594 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)
929 reads
2012-03-08
2,811 reads
Blogs
T-SQL Tuesday #193 – Notes to past and future me
The last T-SQL Tuesday of the year is hosted by my good friend Mike...
A Note and a Message: T-SQL Tuesday #193
By Steve Jones
This month Mike Walsh hosts T-SQL Tuesday. It’s been quite some time since he...
More fun with Git: git restore
The setup My day job involves babysitting a lot of Git repositories hosted on...
Forums
This doesn't make sense to me - making me crazy - er
Hi So I have the below select query that won't return results if I...
Catalog max connection pool size: 100
Seeing this message repeated every 10 seconds in the RSHostingService_yyyy_mm_dd_hh_mm_ss.log file. Can anyone advise:...
CAST datetimeoffset(7) as a datetime in UK format
I have a view where I am casting a datetimeoffset(7) field to smalldatetime or...
Question of the Day
Putting the Player with the Number
In SQL Server 2025, what does this return?
DECLARE @player varchar(20) = 'Bo Nix', @num VARCHAR = '10' SELECT @player || @numSee possible answers