[Solved] Consider the following SQL commands:CREATE TABLE employees(id INT, name TEXT);CREATE INDEX emp_id_hash ON employees USING hash (id);SELECT * FROM employees WHERE id > 5;What is the problem with using... | PostgreSQL

PostgreSQL - Indexing Strategies

Consider the following SQL commands:
CREATE TABLE employees(id INT, name TEXT); CREATE INDEX emp_id_hash ON employees USING hash (id); SELECT * FROM employees WHERE id > 5;
What is the problem with using the hash index in this query?

AThe table must have a primary key before creating a hash index.

BThe index name is invalid for hash indexes.

CHash indexes do not support range queries like <code>id > 5</code>.

DThe query syntax is incorrect for using indexes.

Step-by-Step Solution

Solution:

Step 1: Understand hash index limitations
Hash indexes only support equality searches, not range conditions like id > 5.
Step 2: Analyze the query condition
The query uses a range condition, so the hash index cannot be used efficiently here.
Final Answer:
Hash indexes do not support range queries like id > 5. -> Option C
Quick Check:
Range query + hash index = no use [OK]

Quick Trick: Hash indexes only work with '=' conditions. [OK]

Common Mistakes:

Thinking hash indexes support range queries
Believing index names must follow special rules
Assuming primary key is required for hash index

Master "Indexing Strategies" in PostgreSQL

9 interactive learning modes - each teaches the same concept differently

Learn Why Deep Visual Try Challenge Project Recall Time

Consider the following SQL commands:

Step 1: Understand hash index limitations

Step 2: Analyze the query condition

Final Answer:

Quick Check:

Want More Practice?