Comments on: SQL SERVER – Simple Puzzle Using Union and Union All

By: BD

BD — Tue, 09 Jun 2009 17:22:42 +0000

The first script would result in:

1
1
2

this is because the union part would run first giving:

1
2

then the union all would run giving you:

1
1
2

The second script woudl result in:

1
2

this is because the union all does not eliminate duplicates and results in:

1
1

then the union part runs which eliminates duplicates and gives

1
2

By: Mayank

Mayank — Fri, 23 Jan 2009 07:13:41 +0000

Script 1
1
1
2

Script 2

1
2

By: Karthik.S

Karthik.S — Fri, 20 Jun 2008 11:24:53 +0000

Script 1#
———-
1
1
2

Script 2#
————
1
2

By: geoff

geoff — Wed, 02 Apr 2008 10:04:16 +0000

^
First it will do the UNION ALL so the result set would be
1
1

Next it would do a UNION (so it would do a DISTINCT) so the final result set would be.
1
2

Hope it helps,
geoff

By: ashok

ashok — Thu, 27 Mar 2008 10:31:52 +0000

can u explain how it will produce the result

1
2

thanks,
ashok

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Tue, 25 Mar 2008 18:34:14 +0000

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By: Jerry Hung

Jerry Hung — Tue, 25 Mar 2008 14:20:20 +0000

#1
1
1
2

#2
1
2

I like UNION ALL :)

By: Ranu

Ranu — Tue, 25 Mar 2008 09:40:56 +0000

Answer is
1
1
2

Union All is faster than Union coz… by default Union apply
DISTINCT to remove duplicate record in set
And Union All show all rows including duplicates.

By: Faraz Beg

Faraz Beg — Mon, 24 Mar 2008 18:32:12 +0000

I forgot to mention that i got the first one right without running it… the second one is helped by Query Analyzer… can’t claim a prize then can I ? :-)