How to represent a 2-D data matrix in a database

Question

I have a data set which consists of an ID and a matrix (n x n) of data related to that ID.

Both the column names (A,B,C,D) and the Row names (1,2,3) are also importa

Answer 1

If you want a truly relational solution:

Matrix
------
id

Matrix_Cell
-----------
matrix_id
row
col
value

But constraints to make sure you had valid data would be hideous.

I would consider a matrix as a single value as far as the DB is concerned and store it as csv:

Matrix
------
id
cols
data

Which is somewhat lighter than XML.