Almost anything I can think of which you might use as a natural key could change (disclaimer: not always true, but commonly). An RID is composed of a file number, a page number, and a page's row number. Is the surrogate key the better choice for primary key? The primary key's purpose is to be used internally for distinguishing one row from another. In Figure 1's Purchase table example, if the primary key were CustID plus PurchaseDate, SQL Server would create a 12-byte index key. For example, assume a user table that stores usernames and emails. You still need to prevent logical duplicate data. The criterion that a primary key must be minimal means the fewer the columns, the better. Single responsibility.Unfortunately cars do have a natural key that doesn't change: the VIN (at least in America...)@jcollum Yes ok, that is a fair point. As In organizations in which database development is driven by a group whose primary concern is application development, a natural key is considered the only key to use for a table's primary key. If so, under what circumstances can you use it? With database dialects that don't support clauses like "X inner join Y on X.a = Y.b", or developers who don't use that syntax, the extra joins for surrogate keys do make the queries harder to read, and longer to type and check: see @Tony Andrews post. I've worked on systems with only surrogate keys, and the only drawback has been a lack of denormalised data for partitioning.Most traditional PL/SQL developers I have worked with didn't like surrogate keys because of the number of tables per join, but our test and production databases never raised a sweat; the extra joins didn't affect the application performance.

I get it, but ours do change, and it's a nightmare.In the case of point in time database it is best to have combination of surrogate and natural keys. Here we go again, the old argument still arises... Would we better have a business key as a primary key, or would we rather have a surrogate id (i.e. For example, the Invoice table does not have an OrgName column. Some attributes of a member never change. site design / logo © 2020 Stack Exchange Inc; user contributions licensed under A surrogate key is an artificially produced value, most often a system-managed, incrementing counter whose values can range from 1 to n, where n represents a table's maximum number of rows. I've worked on systems with natural keys, and had to spend a lot of time making sure that value changes would ripple through. does it apply to all rows? Featured on Meta A single-column primary key simplifies data storage, retrieval, and coding. So the logical-key of Organization is OrgName. There is nothing in the normalization rules that suggest that you should store a surrogate integer instead of the value itself.I have three different database books. Create another table called person name and have columns for member_id, member_fname, member_lname, date_updated. There are situations, however, where being in BCNF is very helpful.Agreed.

I think that As it seems that many people present surrogate keys as the almost perfect solution and natural keys as the plague, I will focus on the other point of view's arguments:Use natural keys when it is relevant to do so and use surrogate keys when it is better to use them.Alway use a key that has no business meaning.
Where developers & technologists share private knowledge with coworkersProgramming & related technical career opportunities@Joachim Sauer: An argument about whether a thing is subjective may itself be subjective, without this relating in any way to the objectivity or subjectivity of the thing in question. Instead, customers give you their name, phone number, and perhaps a residence or mailing address. After: Adding planes, boats, bikes and people for load carrying capacity.I guess you don't have any tables where the primary key is composed even partially from 1) any attribute that can and will change), or 2) from user input (e.g. Now you would have to refactor all the child tables PK too. So, anytime they (dimensions) need to be reloaded as new columns are added or need to be populated for all items in the dimension, the SKs assigned during the update makes the SKs out of sync with the original values stored to the fact, forcing a complete reload of all fact tables that join to it.

Instead of wondering if the world has changed and finally a compelling reason to choose one side all times has been provided, it is better to keep asking this question over and over again for each concrete situation, and post to SO when you aren't sure. Surrogate key… Suppose you deal with two businesses named Smith Electronics, one in Kansas and one in Michigan. By using our site, you acknowledge that you have read and understand our "You can always have 2 rows with all the same column values but with a different generated value" so just put a unique or composite unique constraint on your columns.Martin Fowler may be many things, but he isn't an authority on database design.I think you should provide some reasoning before reaching the conclusion. In other words, it does not require adding an additional column or columns. )I'm a fan of using uids for surrogate keys when suitable. Therefore, an RID doesn't meet the criterion that a primary key's value must never change. The CategoryCode column is a derivative of the first column; CategoryCode contains a manufactured code that represents the corresponding long name.

It only has a column for the AccountID. Two reasons:Surrogate keys can be useful when business information can change or be identical.

To state my bias; I'm a developer first, so I'm mainly concerned with giving the users a working application.


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