SQL Join Types
Explore the different SQL join types in PostgreSQL, including inner, outer, cross, and lateral joins. Understand how these operations combine relations to create new datasets and how to apply them in practical queries. This lesson helps you master joining techniques to enhance data retrieval and analysis by leveraging join conditions with meaningful aliases and advanced examples like non-equality joins.
We'll cover the following...
Joins are the basic operations we do with relations. The nature of a join operation is to build a new relation from a pair of existing ones.
The cross join
The most basic join is a cross join or Cartesian product, as we saw in the Boolean truth table, where we built a result set of all possible combinations of all entries.
The equality join
Other kinds of joins associate data between the two relations that participate in the operation. The association is specified precisely in the join condition and is usually based on some equality operator, but it’s not limited to that.