Question

I would like to create a table called “NOTES”. I was thinking this table would contain a “table_name” VARCHAR(100) which indicates what table put in the note, a “key” or multiple “key” columns representing the primary key values of the table that this note applies to and a “note” field VARCHAR(MAX). When other tables use this table they would supply THEIR primary key(s) and their “table_name” and get all the notes associated with the primary key(s) they supplied. The problem is that other tables might have 1, 2 or more PKs so I am looking for ideas on how I can design this…

Answer 1

What you’re suggesting sounds a little convoluted to me. I would suggest something like this.

Notes
------
Id - PK
NoteTypeId - FK to NoteTypes.Id
NoteContent

NoteTypes
----------
Id - PK
Description - This could replace the "table_name" column you suggested

SomeOtherTable
--------------
Id - PK
...
Other Columns
...
NoteId - FK to Notes.Id 

This would allow you to keep your data better normalized, but still get the relationships between data that you want. Note that this assumes a 1:1 relationship between rows in your other tables and Notes. If that relationship will be many to one, you’ll need a cross table.

Have a look at this thread about database normalization

• What is Normalisation (or Normalization)?

Additionally, you can check this resource to learn more about foreign keys

• http://www.w3schools.com/sql/sql_foreignkey.asp