CASSANDRA CQL and Data Modeling 3

Question 1

What does a CQL BATCH statement guarantee in Cassandra?

Accepted Answer

Atomicity for mutations to a single partition (logged batch)

Answer

A logged BATCH in CQL guarantees atomicity (all or nothing) only when all mutations target a single partition; multi-partition batches are strongly discouraged.

Question 2

Which CQL function generates a new unique time-based UUID suitable for use as a clustering key?

Accepted Answer

now()

Answer

The now() function in CQL generates a new TIMEUUID based on the current time, useful for inserting rows with a time-ordered clustering key.

Question 3

In Cassandra, what is 'upsert' behavior?

Accepted Answer

Cassandra always treats INSERT and UPDATE as an upsert — existing rows are overwritten at the cell level

Answer

Cassandra's INSERT and UPDATE both perform cell-level upserts: they write the new value regardless of whether the row exists, with no existence check by default.

Question 4

What is the purpose of the FROZEN keyword in CQL when used with collections or UDTs?

Accepted Answer

Serializes the entire collection/UDT as a single blob, preventing partial updates

Answer

FROZEN serializes the entire collection or user-defined type as a single immutable value; updates must replace the entire value, enabling it to be used as a primary key component.

Question 5

What CQL command is used to examine the current schema of a table, including its primary key and options?

Accepted Answer

DESCRIBE TABLE tablename

Answer

In cqlsh, DESCRIBE TABLE (or DESC TABLE) outputs the full CREATE TABLE statement for the specified table including all columns, types, and table properties.

CASSANDRA - Apache Cassandra Database Practice Test

CASSANDRA - Apache Cassandra Database Practice Test

CASSANDRA CQL and Data Modeling 3