Merge Join
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A merge join is considered one of the fastest methods for joining; it requires both inputs to be sorted. The visualization below shows how the comparison is made. More information can be found here.
Wagner, Bert. “Visualizing Merge Join Internals and Understanding Their Implications.” Data with Bert Atom, https://bertwagner.com/posts/visualizing-merge-join-internals-and-understanding-their-implications/