Why in the world wouldn't you add this information to the database modelling tool used to design the database and create the build script for it?
Obviously that's the ideal situation, but when it doesn't happen, and you inherit the laziness of others, you have to start somewhere. Andy's suggestion is excellent but even it won't solve the problem of those who take shortcuts and leave others with a mess. That is an organisational culture problem, not a technical problem.
There's a special place in hell for people who take credit/bonuses/promotions for passing off undocumented software as if it were a finished product. There is possibly no lower form of programmer.:exclamationmark:
...One of the symptoms of an approaching nervous breakdown is the belief that ones work is terribly important.... Bertrand Russell