Query Planning & Statistics (EXPLAIN ANALYZE) Quiz

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🔍 Postgres Database Administration – Query Planning & Statistics (EXPLAIN ANALYZE)

20 questions · 15 min timer · Explanations included · Free

Which of the following can cause the query planner to choose a nested loop join over a hash join?

A small number of rows in one of the tables being joined.

The use of a complex WHERE clause.

The absence of indexes on the join columns.

The presence of a large number of NULL values in the join columns.

None

A nested loop join may be chosen when one of the tables being joined has a small number of rows, making it efficient to iterate over.

Which of the following scenarios might lead to a sequential scan being chosen over an index scan?

The table is very small, and a sequential scan is more efficient.

The query involves a complex join operation.

The table is frequently updated.

The table has a large number of indexes.

None

For very small tables, a sequential scan might be more efficient than an index scan due to the overhead of using the index.

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