Relationship Between T-Sql And Set Theory

I have always heard that much of t-sql is based on "set theory". I had Set theory in high school and I remember it as being simple Unions, Intersections, Differences of Sets. By a Set I mean a collection such as {2,5,7,8,9, ...) That could well described a single row in a table. By unioning several of these rows we could end up with a table.

But how does that relate to t-sql such as

select * from <table name> Where <condition 1> ?



Is it simply that the result returned by the query is a Set? (if so, a Set is simply being used as a synonym for a Collection. No set theory involved.)



TIA,



barkingdog