1.3.10. Join types (condition) | Lightenna

1.3.10. Join types (condition)

Theta: A_i q B_j
(A from R, B from S)

q is comparison operator
=,<,>,!=,>=
A_i and B_jshare the same domain

Equi: A_i = B_j

Theta join where q is =

Natural: A_i and B_j are the same attribute

in two separate relations (name and domain)
* denotes natural join
e.g. EMPNAMES * DEPENDENTS

Relational join example, equijoin

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