Pailloncy Jean-Gerard <jg@xxxxxxxx> writes:
I do not want for each column and each row to store the value and the unit.
I do want to put the unit in the definition of the column and the check on the parser before any execution.
If you do that, you foreclose the ability to store mixed values in a single column, in return for what? Saving a couple of bytes per value? (I suppose that in a serious implementation we'd store the units as some sort of reference, not as a string.) Compare the implementation of the NUMERIC type: you *can* constrain a column to have a fixed precision, but you do not *have* to.
It strikes me that the right level of constraint is the quantity being represented: length / mass / time / velocity.
Then you could store any of: '1inch', '2m', '3km', '4light-years' in a "length" column.
I was about to say this is similar to the interval type, but of course there are issues there with month/year not being a consistent length.
-- Richard Huxton Archonet Ltd
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