Can we use like in Cassandra?

Since Cassandra 3.4 (3.5 recommended), LIKE queries can be achieved using a SSTable Attached Secondary Index (SASI). A more in depth explanation about how SASI works can be found here.

Which of the following are not allowed in a CQL query?

CQL does not support wildcard queries. CQL does not support Union, Intersection queries. Table columns cannot be filtered without creating the index. Greater than (>) and less than (<) query is only supported on clustering column.

How does Cassandra select query work?

Cassandra provides standard built-in functions that return aggregate values to SELECT statements. A SELECT expression using COUNT(column_name) returns the number of non-NULL values in a column. A SELECT expression using COUNT(*) returns the number of rows that matched the query. Use COUNT(1) to get the same result.

What is the difference between CQL and SQL?

While cQL is similar to SQL as a query language, a key difference is how query results can be returned. In SQL, when tables with “to many” relationships are joined, the row data to the left of the join is duplicated for each joined row. cQL can return objects. It affects the results of queries that use aggregation.

Is Cassandra transactional?

Cassandra supports atomicity and isolation at the row-level, but trades transactional isolation and atomicity for high availability and fast write performance. Cassandra writes are durable.

Can we join two tables in Cassandra?

You cannot perform joins in Cassandra. If you have designed a data model and find that you need something like a join, you’ll have to either do the work on the client side, or create a denormalized second table that represents the join results for you. This latter option is preferred in Cassandra data modeling.

How do you add multiple values in Cassandra?

There is a batch insert operation in Cassandra. You can batch together inserts, even in different column families, to make insertion more efficient. In Hector, you can use HFactory. createMutator then use the add methods on the returned Mutator to add operations to your batch.

What is the purpose of using thrift in Cassandra?

Thrift is actually an RPC protocol or API unified with a code generation tool for CQL, and the purpose of using thrift in Cassandra is because it facilitates easy access to Database (DB), across the Programming Language.

Is Cassandra better than SQL?

Cassandra is able to handle high storage. SQL is able to handle moderate storage. As Cassandra facilitates automatic distribution of data, it allows relatively fast data transfer to or from the storage. SQL features a fixed schema and hence, it indicates limitations in the database storage.

Why is CQL needed?

Cassandra allows you to replicate your data to other data centers and keep multiple copies in multiple locations. This helps satisfy many regulatory requirements in addition to being a part of a strong disaster recovery and business continuity plan.

Is Cassandra good for OLTP?

But Cassandra writes are extremely fast which is good for OLTP. I can use C* for OLAP because reads are extremely fast which is good for reporting too.

Which is more specific select or where in CQL?

WHERE clause is a bit more specific than SELECT. In SELECT the user selects a field, whereas in WHERE clause the user can select a particular data. In other words, the data is specific to a particular cell of a table. This clause is used along with SELECT cause, in which WHERE acts as a condition.

Which is the correct way to use cqlsh in Cassandra?

The following table explains all the options of cqlsh and their usage. Shows help topics about the options of cqlsh commands. Provides the version of the cqlsh you are using. Directs the shell to use colored output. Shows additional debugging information. Directs the shell to accept and execute a CQL command.

What is the default number of rows in cqlsh?

The cqlsh shell has a default row limit of 10,000. The Cassandra server and native protocol do not limit the number of returned rows, but they apply a timeout to prevent malformed queries from causing system instability. The WHERE clause introduces one or more relations that filter the rows returned by SELECT.

What do I need to know before starting cqlsh?

The CQL version displays after starting cqlsh. Show additional debugging information. Disables saving history to disk for current execution. Specify a specific DSE protocol version; otherwise the client will default and downgrade as necessary. Mutually exclusive with –protocol-version.