Join multiple table
Introduction When joining multiple tables together (such as 3 tables or more), PostgreSQL never joins all tables at the same time, but at any single point in time, it can only join 2 datasets. Suppose you need to join multiple tables, the process of bridging steps will be performed as follows First, Postgres will select 2 tables to join together to create an Intermediate Result Postgres will treat the Intermediate Result as a completely new table and will use it to join with the next table to create the next Intermediate Result This process repeats over and over until all tables have been joined. Algorithms used When joining multiple tables, Postgres still uses algorithms like Nested Loop Join, Hash Join and Merge Join But corresponding to each dataset and the index of the tables, Postgres will choose different algorithms when joining rather than fixing a single algorithm For example, when joining 4 tables A, B, C and D together Suppose table A is small with about 100 rows joining with...