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INT versus GUID on a table's primary key

, 6 May 2008 CPOL
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This article tries to show the pros and cons of using INT or GUID types on primary keys.


This article shows the pros and cons of using the INT or GUID types on primary keys. Hope it helps you decide which suites your project best.

Using INT on primary keys

  • Small amount of storage size (and integer is 4 bytes).
  • Increased readability, practical use in testing, and easy to remember.
  • Chronology of data; if two records are in ascending order, we can deduce that the second record was inserted after the first one.
  • Support for functions that return the last primary key generated (@@IDENTITY, SCOPE_IDENTITY()).
  • Difficulty in the case of merging tables (the need to make remapping because the primary keys may be duplicated).
  • Hard to work with distributed tables.
  • Primary key in the form of INT/BIGINT is LUID, local unique identifier, which is only used locally in a table.
  • After a large number of operations (insert, delete), the counter for primary key can be reset, bringing the problem of chronology to 1.

Using GUID on primary keys

  • Easy to merge tables.
  • Easy to work with distributed tables.
  • The primary key is uniquely identified in the entire system (the number of machines or tables doesn't matter).
  • Don't have problems when inserting a large number of operations.
  • Bigger storage size (16 bytes - four times the size of an integer).
  • Don't have the chronology assumption.
  • Hard to remember and use in testing.
  • Don't benefit from a mechanism to obtain the last generated primary key (MS SQL Server).

My decision

I had a hard time deciding which solution suites best for my project, but I finally used GUIDs because of the advantages mentioned. But this happened only once, the rest of my projects have databases with INT primary keys. Hope someone finds this useful. Special thanks to Iancu Caputa for helping with this article.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Liviu Holhos
Software Developer
Romania Romania
Web developer, designer and basketball enthusiast.
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Comments and Discussions

QuestionGreat article, but missing one important thing. PinmemberDaniel Carnielli21-Nov-12 5:36 
Generalok but PinmemberDonsw14-Jun-09 16:30 
QuestionComposite PK on two integer fields? Pinmemberpashaper11-Nov-08 23:22 
GeneralGUIDs fragmentation PinmemberGeyzerskiy Dmitriy8-May-08 2:45 
GeneralRe: GUIDs fragmentation [modified] PinmemberLiviu Holhos8-May-08 21:42 
GeneralRe: GUIDs fragmentation PinmemberMike Lang13-May-08 3:54 
GeneralRe: GUIDs fragmentation PinmemberLiviu Holhos13-May-08 21:05 
GeneralRe: GUIDs fragmentation PinmemberGeyzerskiy Dmitriy13-May-08 23:48 
QuestionWhat about Performance PinmemberDoug K. Wilson7-May-08 18:07 
AnswerRe: What about Performance PinmemberLiviu Holhos7-May-08 20:46 
Performance wasn't an issue for me, I mean the cost of maintenance vs. the performance is tricky. If you need speed and don't have the problems I've mentioned in Disadvantages section for INT's, you should probably use INT's.
I've tested once the performance fetching 1.000.0000 GUIDs on a 1.5 GHz with 1GB RAM. I used two techniques of generating the GUIDs:
1) NEWID()
(algorithm named COMBs, by Jimmy Nilsson)
The results were the following:
1) fetching 1.000.0000 GUIDs was 10 times consuming than fetching 1.000.0000 INTs
2) fetching 1.000.0000 GUIDs was 1.2 times consuming than fetching 1.000.0000 INTs (almost the same)
After this test I was convinced that using GUIDs was the best solution for my project, since I've kinda needed the advantages specified. The best thing to do is take a shot and test this yourself, see what results you get.
GeneralRe: What about Performance Pinmemberastanton197820-May-08 2:50 

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