Quick and dirty way to make a very large table

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Quick and dirty way to make a very large table

GabyYYZ

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August 28, 2008 at 9:38 am

#211901

Comments posted to this topic are about the item Quick and dirty way to make a very large table
Gaby________________________________________________________________"In theory, theory and practice are the same. In practice, they are not." - Albert Einstein

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Jeff Moden SSC Guru Points: 1004318 More actions · Answer 1

Gaby,

Ok... I realize that you said "quick and dirty", but I keep looking at this article and wondering... why? :blink: Why would someone need to generate a giga-byte sized test table with virtually no useful test data in it? The only thing I can think of (maybe) is to use it for testing backups.

And, that's a lot of RBAR in that code... it can be done without any RBAR using the following...

--===== If the test table already exists, drop it so we can rebuild it

IF OBJECT_ID('dbo.BigTable','U') IS NOT NULL

DROP TABLE dbo.BigTable

GO

--===== Define a handful of dynamic SQL variables

DECLARE @SQL1 VARCHAR(8000),

@SQL2 VARCHAR(8000),

@SQL3 VARCHAR(8000)

--===== Define the "fixed" portion of the SELECT list

SELECT @SQL1 = '

SELECT TOP 265000

IDENTITY(INT,1,1) AS RowID,

GETDATE() AS EntryDate,

' + CHAR(9)

--===== Define the 220 GUID columns we want to build.

-- This uses the variable overlay technique of concatenation.

SELECT @SQL2 = COALESCE(@SQL2+','+CHAR(10)+ CHAR(9),'') + 'NEWID() AS Val' + CAST(Number AS VARCHAR(10))

FROM Master.dbo.spt_Values --Could use a Tally or Numbers table here

WHERE Type = 'P'

AND Number BETWEEN 1 AND 220

--===== Define the "Into" and the cross join that will spawn the rows.

-- This uses the same cross-join technique usefull in building Tally and Numbers tables

SELECT @SQL3 = '

INTO dbo.BigTable

FROM Master.dbo.SysColumns sc1 WITH (NOLOCK)

CROSS JOIN Master.dbo.SysColumns sc2 WITH (NOLOCK)'

--===== Show what the final code looks like, just for fun...

-- PRINT @SQL1+@SQL2+@SQL3

--===== ... and then run it. (Takes about a minute on my ancient but useful box)

EXEC (@SQL1+@SQL2+@SQL3)

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

GabyYYZ SSCertifiable Points: 7913 More actions · Answer 2

Hmmm...true. 🙂 Ran it very quickly on my box as well.

I discovered one more way to create a big table a day or so after submitting my script. Create your table with one dummy_column as default null (or default getdate()) and the rest default newid() columns.

Insert 1 row into the table with default values then loop it as so:

insert bigtable default values

set @ctr = 0

set @num_iterations = 18 -- this is a DOUBLING number, so anything past 18 and you're getting into slow territory.

while @ctr < @num_iterations

begin

insert into bigtable(dummy_column)

select dummy_column from bigtable

set @ctr = @ctr + 1

end

Dummy_column can be anything, including null, as long as the other columns have default newid() set. This is also pretty quick way to create a large table.

Gaby________________________________________________________________"In theory, theory and practice are the same. In practice, they are not." - Albert Einstein

Jeff Moden SSC Guru Points: 1004318 More actions · Answer 3

You still haven't answered the question though... why would anyone create such a table of 1 gig of almost nothing but NEWID()'s?

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

GabyYYZ SSCertifiable Points: 7913 More actions · Answer 4

Jeff Moden (9/5/2008)
You still haven't answered the question though... why would anyone create such a table of 1 gig of almost nothing but NEWID()'s?

I guess it was to generate a large enough backup for a third-party backup utility (i.e. Litespeed) to see how it performed. Didn't want to toy with any production servers.

Gaby________________________________________________________________"In theory, theory and practice are the same. In practice, they are not." - Albert Einstein

Jeff Moden SSC Guru Points: 1004318 More actions · Answer 5

Thanks, Gaby... 🙂

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)