Join (Relational Algebra)

relational-algebra

Definition

Join (Relational Algebra)

Joins are a way to associate two relations $R$ and $S$ based on certain conditions.

Commutativity

In relational algebra, joins are never commutative given that the schema of a join depends on the order, e.g.:

$$\text{sch}(R\bowtie S)\ne \text{sch}(S\bowtie R)$$