What is a CQL query in Cassandra?
In this article, we are going to discuss CQL query which is very useful to create, insert, delete, manipulate, filtering data etc. Let’s discuss how we can write the better CQL query for these operations. CQL is used to create, insert, manipulate data in Cassandra.
What is the difference between find() and select * in Cassandra?
In the above example it will perform the query SELECT * FROM person WHERE name=’john’ but find () allows you to perform even more complex queries on cassandra. You should be aware of how to query cassandra.
What is the flexible data model in Cassandra?
Flexible Data Model – The concepts from DynamoDB and BigTable are built into Cassandra to allow for complex data structures. The model works for a wide variety of data modeling use cases. Linearly Scalable – When new nodes are added, the data is more evenly distributed across the nodes, which reduces the load each node handles.
What is the difference between relational database and Cassandra?
In relational databases, the database schema is first created and then queries are created around the DB Schema. In Cassandra, schema design should be driven by the application queries. In relational databases, data normalization is a best practice, but in Cassandra data duplication is encouraged to achieve read efficiency.
How to update the data in the Cassandra table?
Command ‘Update’ is used to update the data in the Cassandra table. If no results are returned after updating data, it means data is successfully updated otherwise an error will be returned. Column values are changed in ‘Set’ clause while data is filtered with ‘Where’ clause.
How do I trace a read and write in Cassandra?
Cassandra 1.2 introduced a new request tracing capability that will allow you to track the progression of reads and writes throughout Cassandra. To view traces, fire up cqlsh on one of your Cassandra nodes and run the following command: cqlsh> tracing on; Now tracing requests.
What happens when you delete a row in Cassandra?
Cassandra Delete Data Command ‘Delete’ removes an entire row or some columns from the table Student. When data is deleted, it is not deleted from the table immediately. Instead deleted data is marked with a tombstone and are removed after compaction.