UNION ALL Optimization

Question

UNION ALL Optimization

ralahari

Old Hand

Points: 301
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June 19, 2024 at 7:26 pm

#4429811

select Colum1 , Colum2 from table 1
Union All
select Colum1 , Colum2 from table 2
Union All
select Colum1 , Colum2 from table 3
How to Optimize above 3 Queries into one.

Viewing 7 posts - 1 through 6 (of 6 total)

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ScottPletcher SSC Guru Points: 101095 More actions · Answer 1

Combining them wouldn't optimize it. For three different tables, SQL must still scan each table/covering index to provide the results.

SQL DBA,SQL Server MVP(07, 08, 09) "It's a dog-eat-dog world, and I'm wearing Milk-Bone underwear." "Norm", on "Cheers". Also from "Cheers", from "Carla": "You need to know 3 things about Tortelli men: Tortelli men draw women like flies; Tortelli men treat women like flies; Tortelli men's brains are in their flies".

Jonathan AC Roberts SSCoach Points: 18354 More actions · Answer 2

ralahari wrote:

How to Optimize above 3 Queries into one.

It already is one query.

ralahari Old Hand Points: 301 More actions · Answer 3

I am looking for With out Union all how to achieve same Query o/p. Any helps highly Appreciated.

Jonathan AC Roberts SSCoach Points: 18354 More actions · Answer 4

ralahari wrote:

I am looking for With out Union all how to achieve same Query o/p. Any helps highly Appreciated.

Why would you want to do it without a union and in just one query?

Jonathan AC Roberts SSCoach Points: 18354 More actions · Answer 5

.

This reply was modified 5 months ago by Jonathan AC Roberts. Reason: deleted duplicate post

Emperor100 SSCrazy Points: 2173 More actions · Answer 6

@ralahari:

Paste your query and execution plan with data if possible. Understand that, there are many variables that we need to look into to optimize a query

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