[Solved] What is the main difference between a sequential scan and an index scan in PostgreSQL? — Ans: Sequential scan reads the entire table; index scan uses an index to find rows. | PostgreSQL

PostgreSQL - Performance Tuning

What is the main difference between a sequential scan and an index scan in PostgreSQL?

ASequential scan uses an index; index scan reads the entire table.

BSequential scan reads the entire table; index scan uses an index to find rows.

CSequential scan only works on small tables; index scan only on large tables.

DSequential scan is faster than index scan in all cases.

Step-by-Step Solution

Solution:

Step 1: Understand sequential scan behavior
A sequential scan reads every row in the table to find matching rows.
Step 2: Understand index scan behavior
An index scan uses an index to quickly locate matching rows without reading the whole table.
Final Answer:
Sequential scan reads the entire table; index scan uses an index to find rows. -> Option B
Quick Check:
Scan type difference = A [OK]

Quick Trick: Sequential scan reads all rows; index scan uses index to jump [OK]

Common Mistakes:

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What is the main difference between a sequential scan and an index scan in PostgreSQL?