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Join Algorithms interview questions

18 real Join Algorithms questions from the SQL bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.

1. What is Nested loop join?

Mid
  1. A.an algorithm that scans the outer input and, for each row, probes the inner input, ideal when one side is small or indexed
  2. B.a distributed strategy that copies a small table to every node so each can join its local partition without reshuffling
  3. C.an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
  4. D.the sequence in which the optimizer combines tables, chosen to keep intermediate result sizes as small as possible
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3. Which statement is correct?

Mid
  1. A.Nested loop join — an algorithm that consumes two inputs already sorted on the key and advances through them in lockstep to match rows
  2. B.Nested loop join — an algorithm that scans the outer input and, for each row, probes the inner input, ideal when one side is small or indexed
  3. C.Nested loop join — a distributed strategy that repartitions both inputs on the join key across nodes so matching rows land together
  4. D.Nested loop join — the sequence in which the optimizer combines tables, chosen to keep intermediate result sizes as small as possible
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4. What is Hash join?

Mid
  1. A.an algorithm that consumes two inputs already sorted on the key and advances through them in lockstep to match rows
  2. B.the sequence in which the optimizer combines tables, chosen to keep intermediate result sizes as small as possible
  3. C.an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
  4. D.a distributed strategy that repartitions both inputs on the join key across nodes so matching rows land together
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5. Which term means: "an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins"?

Mid
  1. A.Nested loop join
  2. B.Partitioned join
  3. C.Hash join
  4. D.Merge join
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6. Which statement is correct?

Mid
  1. A.Hash join — the sequence in which the optimizer combines tables, chosen to keep intermediate result sizes as small as possible
  2. B.Hash join — an algorithm that scans the outer input and, for each row, probes the inner input, ideal when one side is small or indexed
  3. C.Hash join — an algorithm that consumes two inputs already sorted on the key and advances through them in lockstep to match rows
  4. D.Hash join — an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
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7. What is Merge join?

Mid
  1. A.an algorithm that consumes two inputs already sorted on the key and advances through them in lockstep to match rows
  2. B.a distributed strategy that copies a small table to every node so each can join its local partition without reshuffling
  3. C.the sequence in which the optimizer combines tables, chosen to keep intermediate result sizes as small as possible
  4. D.an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
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9. Which statement is correct?

Mid
  1. A.Merge join — an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
  2. B.Merge join — an algorithm that scans the outer input and, for each row, probes the inner input, ideal when one side is small or indexed
  3. C.Merge join — a distributed strategy that repartitions both inputs on the join key across nodes so matching rows land together
  4. D.Merge join — an algorithm that consumes two inputs already sorted on the key and advances through them in lockstep to match rows
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10. What is Join order?

Senior
  1. A.an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
  2. B.the sequence in which the optimizer combines tables, chosen to keep intermediate result sizes as small as possible
  3. C.an algorithm that consumes two inputs already sorted on the key and advances through them in lockstep to match rows
  4. D.a distributed strategy that copies a small table to every node so each can join its local partition without reshuffling
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12. Which statement is correct?

Senior
  1. A.Join order — a distributed strategy that copies a small table to every node so each can join its local partition without reshuffling
  2. B.Join order — an algorithm that consumes two inputs already sorted on the key and advances through them in lockstep to match rows
  3. C.Join order — the sequence in which the optimizer combines tables, chosen to keep intermediate result sizes as small as possible
  4. D.Join order — a distributed strategy that repartitions both inputs on the join key across nodes so matching rows land together
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13. What is Broadcast join?

Senior
  1. A.a distributed strategy that copies a small table to every node so each can join its local partition without reshuffling
  2. B.a distributed strategy that repartitions both inputs on the join key across nodes so matching rows land together
  3. C.an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
  4. D.the sequence in which the optimizer combines tables, chosen to keep intermediate result sizes as small as possible
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15. Which statement is correct?

Senior
  1. A.Broadcast join — an algorithm that consumes two inputs already sorted on the key and advances through them in lockstep to match rows
  2. B.Broadcast join — an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
  3. C.Broadcast join — a distributed strategy that copies a small table to every node so each can join its local partition without reshuffling
  4. D.Broadcast join — a distributed strategy that repartitions both inputs on the join key across nodes so matching rows land together
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16. What is Partitioned join?

Senior
  1. A.an algorithm that scans the outer input and, for each row, probes the inner input, ideal when one side is small or indexed
  2. B.an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
  3. C.a distributed strategy that copies a small table to every node so each can join its local partition without reshuffling
  4. D.a distributed strategy that repartitions both inputs on the join key across nodes so matching rows land together
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18. Which statement is correct?

Senior
  1. A.Partitioned join — a distributed strategy that copies a small table to every node so each can join its local partition without reshuffling
  2. B.Partitioned join — an algorithm that consumes two inputs already sorted on the key and advances through them in lockstep to match rows
  3. C.Partitioned join — an algorithm that builds an in-memory hash table on one input and probes it with the other, favored for large unsorted equality joins
  4. D.Partitioned join — a distributed strategy that repartitions both inputs on the join key across nodes so matching rows land together
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