The default index type for MEMORY tables is . . . . . . . .

Solution (By Examveda Team)

This question asks about the type of index that is automatically used for tables created with the MEMORY storage engine in MySQL.

MEMORY tables store data in RAM, which makes them very fast for reading but less reliable because the data is lost when the server restarts.

The options provided are different types of indexes:

* HASH: Uses a hash function for quick lookups, but doesn't support range queries (like finding values between two numbers).
* SPATIAL: Used for indexing geographic data (like coordinates) to enable efficient spatial queries.
* FULLTEXT: Used for indexing text data to enable fast searching of words within the data.
* UNIQUE: Ensures that each value in a column is unique.

The answer is Option A: HASH. MEMORY tables by default use HASH indexes. This is because HASH indexes are very efficient for lookups and don't require extra disk space.