If you are worried about fragmentation, do you have a maintenance solution on your server that addresses that such as SQL Server Maintenance Solution - Ola Hallengren?
- datetime data type is date, smalldatetime, datetime, datetime2(0-2),datetime2(3-4), datetime(5+) or?
- LocationId data type is tinyint, smallint, int, bigint or ?
- Character code data type is char(2), nchar(2) or?
- How many rows are in your table?
- Would you need an int or bigint for a surrogate id?
- What are the other columns in your table?
- Are all queries filtered by datetime, or are filtered by the locationid and/or character code?
- Are you always returning the whole row, or sometimes just pieces of it?
Because most people assume the Primary Key is the Clustering Key, I am going to interpret your question as "How to index a composite clustering key with non-sequential inserts?".
The situation you are considering is related to debates like The Clustered Index Debate and Surrogate Key vs. Natural Key.
In this situation, I would want to consider the impact of a [16?] byte composite clustering key vs a 4 or 8 byte clustering key (int / bigint). My decision tree would look something like this:
Will we be using Hekaton (In-Memory OLTP)?
How many rows will this table have?
How will the table be queried?
Various combinations of and not always all of
datetime, location_id, character_code => surrogate key.
- In this case you may want to be able to have multiple supporting indexes the combinations of
datetime, location_id, character_code for your queries.
The clustering key is included in all non-clustered indexes, and the larger it is the more space/pages each index entry will require. => surrogate key.
Almost always by all three
datetime, location_id, character_code or almost always by
but not by
datetime and not
datetime, location_id (zero or only a couple of non-clustered indexes on this table) => continue...
Will any other table reference this table?
Even if my first run through of the above decision tree leads me to a composite key, I would probably start my design using a surrogate key because it is easier to get rid of it (because it isn't being used) than to go back and add it and implement its use.
Just to clarify, I have had cases where I did find that the composite key was a better solution and did refactor the design to drop the surrogate key. I don't want to leave the impression that the surrogate key is always the better solution, even if it is a common default for many designers (including myself).