It's true that Codd and Date used the term 'relational' (They championed the N-ary Relational Model - others were around at the same time) but it's not easy to track the origin of the term in mathematics. Certainly the word implies joining things together. I guess the joining refers to fields (domains) within each row (n-tuple).
If you look at other forums you often see novices (and others) using the word 'relate' as if it is some special way of joining information between two tables. They also clearly feel that you need to declare foreign keys in order to have a logical connection between tables. As you are no doubt aware, one of the guiding principles of the relational model is there is nothing that is not a data value so you are totally free to join anything to anything as long as you feel it might make sense. Relationships between tables are contingent - they can be there one day and gone the next. Any persistent relationship information (eg foreign keys) is optional and there for other purposes (eg documentation or referential integrity enforcement). Another common conceptual misunderstanding I've seen over the years is that the database is just a fancy filestore. There are still people who just want a cursor to a chunk of data which they pull in and iterate over rather than use SQL's power to manage data a set-at-a-time. Call me old fashioned but object-relational mappers worry me on this score. -- View this message in context: http://www.nabble.com/What-is-a-Relation--tp24674278p24681797.html Sent from the SQLite mailing list archive at Nabble.com. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
