Question

Because I have a poor memory, I want to write a simple application to store table column information, especially the meaning of table columns. Now I have a problem with my table design. I plan to make the table have the following columns:

id, table_name, column_name, data_type, is_pk, meaning

But this design can’t express the foreign key relationship. For example: table1.column1 and table2.column3 and table8.column5 all have the same data type and the same meaning, how can I modify my table design to express this information(relationship)?

Great thanks!

PS:
In fact, recently I’m working on a legacy application. The database is poorly designed. The foreign key relationship is not expressed on the database layer but on the application layer. Now my boss not allow us to modify the database. We just need to make the application working. So I can’t do some work on the database directly.

Answer 1

Depending on your DBMS, you could probably use comments on the table / column to record the meaning of each one of those columns. Most DBMS allow you to perform some kind of annotation.

If you must have it in your table you have a few choices.

• Free text If this is just to serve as a memory aid, it doesn’t really need to be machine readable. This makes it easier for you to read / use directly.
• fk_id Store the ID of the field this foreign key maps into. You could then define a view that pulls in the meaning column from this foreign key.
• Meaning Table Store meaning as an ID into a seperate table and use a view to make it easier to work with.
• Create a document Keep it in a document instead. That way you can print it out and have it handy.

You could try designing a full de-normalized schema for this, but I’d argue thats seriously over-thinking something that’s just meant as a memory aid.