Join and Cross

In this example, we will use a self join. We create two relations and rename them and then apply the operators join, cross, union and except

[[nom::foo]] [[type::selective]] [[amount::500000]]
[[nom::foo]] [[type::automatic]] [[amount::400000]]
[[nom::bar]] [[type::selective]] [[amount::300000]]
[[nom::ccc]] [[type::selective]] [[amount::250000]]
[[nom::ddd]] [[type::automatic]] [[amount::150000]]

Note that in relations, tuples are sets and have no predefined orders of their parameters.

The same note on relations apply. The returned relation from UNION has tuples with the same parameters, but not in a particular order.