What is the difference between a hash join and a nested loop join in query execution?

Question

Advanced SQL Developer — Medium

What is the difference between a hash join and a nested loop join in query execution?

Accepted Answer

A hash join builds a hash table from the smaller table and probes it with the larger table, making it efficient for large unsorted equi-joins without suitable indexes. On the other hand, a nested loop join iterates each row of the outer table checking matching rows in the inner table, which is efficient when the inner table is small or well-indexed.