The Simplest Join — Nested-Loops

• Requires two nested loops:

  For each tuple in outer relationFor each tuple in inner, compareIf match on join attribute, output
  

• Block nested loops join: read & match page at a time

• What if join attributes are indexed?

  Index nested-loops join
  

• Very simple to implement

• Inefficient if size of inner relation > memory (keep swapping pages); requires sequential search for match

Join

outer

inner

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