Hash Match builds and populates a hash table, passing the result onto the next step.
Hash Matches can be used in Joins, Distinct or Aggregates, and Union operations. The hash table is built and then populated from the first input. The second input is then used to match values already in the table. At the end of the operation, all rows are passed onto the next step.
- Microsoft Documentation - Showplan Logical and Physical Operators Reference
- Microsoft Documentation - Explain Plans
- Plansplaining - Hugo Kornelis' Blog series
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