Comment by another2another

You can actually get quite some way by adding constraints to columns. NOT NULL, default values and a CHECK constraints on a column can limit random invariance bleeding into the db.

So for example, if I ever see a CHAR(1) column that looks like it's meant to hold a boolean of some sort, the best thing is to immediately lock it down to a strict subset (preferably not NULL) of 2 states like ['Y'|'N'].

I still have nightmares about a db schema that grew a fungus of boolean representations, and massive amounts of code checking for y,n,Y,N,0,1,T,F,t,f all of which were used by different teams at different times. Constraints would have stopped all that.

Here's the docs for Postgres: https://www.postgresql.org/docs/current/ddl-constraints.html