Re: Maximum number of columns in a table

Martin Gainty <mgainty@xxxxxxxxxxx> · Sat, 11 Apr 2009 16:29:09 -0400

Thats alot of columns
you might want to normalise your data before settling on any feeding a fixed DB schema

http://www.datamodel.org/NormalizationRules.html
1)

Are there any repeating patterns? such as Repeating Groups or Redundant data e.g.
OrderLineItem1...OrderLineItem2
splitting the grouping of (related data points) such as OrderLineItems to a new table would allow you to creating a unique key such as OrderLineItemID (foreign key in your table) to point to uniquely access only the related data points from your new table

2)
Are there any data columns that do not necessarily absolutely belong in the data?
I once worked with Patient Data where someone put Patient phone number in Diagnosis
(Patient's diagnosis has nothing to do with their phone unless the bill is off the charts)
Diagnosis belongs with Patient DRG code and Diagnostic Physician Name
Patient Phone number is more closely associated with Contact record for that Patient

Up front schema design is vital and necessary activity for ensuring you know how your data can be aggregated into functional groups before

1)Any Database/Table Creation (or any DB entity is created)
2)Any data Feeds from external sources or Form Population to your new DB entities
take place..

HTH
Martin 
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From: gerry@xxxxxxxxxx
To: pgsql-general@xxxxxxxxxxxxxx
Subject: [GENERAL] Maximum number of columns in a table
Date: Sun, 12 Apr 2009 05:33:35 +1000

The FAQs state "Maximum number of columns in a table? 250-1600 depending on column types".

Is there a location which gives instructions for calculating whether a number of columns of different types can be accommodated?

I have a situation where I need to load tables from another database which may theoretically contain up to 1000 columns per table and this information will determine whether I need to rebuild PostgreSQL with a larger blocksize.  Splitting into multiple tables is not always an easy option.

Many thanks

Gerry 

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