Hash join is not a nested loop, it's two separate loops one after the other. This makes a huge difference since the complexity is O(N+M) rather than O(N*M). See

Hash join is not a nested loop, it's two separate loops one after the other. This makes a huge difference since the complexity is O(N+M) rather than O(N*M). See these examples: https://vladmihalcea.com/hash-join-algorithm/ https://vladmihalcea.com/hash-join-algorithm/ https://vladmihalcea.com/nested-loop-join-algorithm/ https://vladmihalcea.com/nested-loop-join-algorithm/