Hi
http://www.postgresql.org/docs/current/static/datatype-boolean.html states:
The boolean type can have one of only two states: "true" or
"false". A third state, "unknown", is represented by the SQL null value.
This sounds like an oxymoron to me. Perhaps that sentence should be
changed to:
The boolean type can have one of three states: "true" or
"false" and "unknown". The third state, "unknown", is represented by the
SQL null value.
or:
The boolean type can have one of three states: "true" or
"false" and null. The third state, null, represents the logical value
"unknown".
Best regards
Jack Douglas
