I am wondering if there is a best coding practice in regard to dealing with IDs for parent > child objects in the code, where the DB records use an auto incremented int as the ID (on the initial save). Of course when in the code you are unable to guess what this ID might be and therefore must leave it blank and presumably save all these items in a transaction grabbing the parent ID first and then setting it on all children before saving them
Guids on the other hand are much easier to deal with in the code, as of course you can happily generate the Id first and set it on everything and save without worry..
is there a nice easy way to deal with objects in code using auto-ints as their db keys?
thanks
int is smaller, faster, easy to remember, keeps a chronological sequence. And as for Guid , the only advantage I found is that it is unique. In which case a Guid would be better than and int and why? From what I've seen, int has no flaws except by the number limit, which in many cases are irrelevant.
GUIDs can be considered as global primary keys. Local primary keys are used to uniquely identify records within a table. On the other hand, GUIDs can be used to uniquely identify records across tables, databases, and servers.
Considering that a GUID is in essence a 128 bit INT and a normal INT is 32 bit, the INT is a space saver (though this point is generally moot in most modern systems). In the end, in what circumstances would you see yourself using an INT as a PK versus a GUID?
GUIDs may seem to be a natural choice for your primary key - and if you really must, you could probably argue to use it for the PRIMARY KEY of the table. What I'd strongly recommend not to do is use the GUID column as the clustering key, which SQL Server does by default, unless you specifically tell it not to.
GUIDs may seem to be a natural choice for your primary key - and if you really must, you could probably argue to use it for the PRIMARY KEY of the table. What I'd strongly recommend not to do is use the GUID column as the clustering key, which SQL Server does by default, unless you specifically tell it not to.
You really need to keep two issues apart:
1) the primary key is a logical construct - one of the candidate keys that uniquely and reliably identifies every row in your table. This can be anything, really - an INT, a GUID, a string - pick what makes most sense for your scenario.
2) the clustering key (the column or columns that define the "clustered index" on the table) - this is a physical storage-related thing, and here, a small, stable, ever-increasing data type is your best pick - INT or BIGINT as your default option.
By default, the primary key on a SQL Server table is also used as the clustering key - but that doesn't need to be that way! I've personally seen massive performance gains when breaking up the previous GUID-based Primary / Clustered Key into two separate key - the primary (logical) key on the GUID, and the clustering (ordering) key on a separate INT IDENTITY(1,1) column.
As Kimberly Tripp - the Queen of Indexing - and others have stated a great many times - a GUID as the clustering key isn't optimal, since due to its randomness, it will lead to massive page and index fragmentation and to generally bad performance.
Yes, I know - there's newsequentialid()
in SQL Server 2005 and up - but even that is not truly and fully sequential and thus also suffers from the same problems as the GUID - just a bit less prominently so.
Then there's another issue to consider: the clustering key on a table will be added to each and every entry on each and every non-clustered index on your table as well - thus you really want to make sure it's as small as possible. Typically, an INT with 2+ billion rows should be sufficient for the vast majority of tables - and compared to a GUID as the clustering key, you can save yourself hundreds of megabytes of storage on disk and in server memory.
Quick calculation - using INT vs. GUID as Primary and Clustering Key:
TOTAL: 25 MB vs. 106 MB - and that's just on a single table!
Some more food for thought - excellent stuff by Kimberly Tripp - read it, read it again, digest it! It's the SQL Server indexing gospel, really.
Also: from a C# / .NET point of view - it depends on how you access your SQL Server database. If you use something like Linq-to-SQL or Entity Framework v4, your .NET objects will be automagically updated with the inserted IDs (from your INT IDENTITY
column) - without you having to do anything at all. So to me, that's one less reason why you should feel the need to use GUID's....
GUID's are horribly bad as SQL Server clustering keys - not just bad - really, truly, AWFUL
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