Surrogate vs. natural/business keys [closed]

Answer 1

I hate surrogate keys in general. They should only be used when there is no quality natural key available. It is rather absurd when you think about it, to think that adding meaningless data to your table could make things better.

Here are my reasons:

1. When using natural keys, tables are clustered in the way that they are most often searched thus making queries faster.

2. When using surrogate keys you must add unique indexes on logical key columns. You still need to prevent logical duplicate data. For example, you can’t allow two Organizations with the same name in your Organization table even though the pk is a surrogate id column.

3. When surrogate keys are used as the primary key it is much less clear what the natural primary keys are. When developing you want to know what set of columns make the table unique.

4. In one to many relationship chains, the logical key chains. So for example, Organizations have many Accounts and Accounts have many Invoices. So the logical-key of Organization is OrgName. The logical-key of Accounts is OrgName, AccountID. The logical-key of Invoice is OrgName, AccountID, InvoiceNumber.

   When surrogate keys are used, the key chains are truncated by only having a foreign key to the immediate parent. For example, the Invoice table does not have an OrgName column. It only has a column for the AccountID. If you want to search for invoices for a given organization, then you will need to join the Organization, Account, and Invoice tables. If you use logical keys, then you could Query the Organization table directly.

5. Storing surrogate key values of lookup tables causes tables to be filled with meaningless integers. To view the data, complex views must be created that join to all of the lookup tables. A lookup table is meant to hold a set of acceptable values for a column. It should not be codified by storing an integer surrogate key instead. There is nothing in the normalization rules that suggest that you should store a surrogate integer instead of the value itself.

6. I have three different database books. Not one of them shows using surrogate keys.