"Equi" and "Natural" join
Equi-join: Common attributes are compared for equality
- no need to specify a join condition
- could join on more than one attribute
- need to list attributes if names are not the same
- superfluous column of 2nd relation removed
- "Natural join": Equi-join on all common fields
Notation (some texts): R1 * attr-lists R2
When people say “join” natural join is usually what they mean.