Cassandra is a database with its own language for query called Cassandra Query Language (CQL). It’s a declarative language for communicating with Cassandra–developers use CQL commands to write and read data from the database.
CQL’s easy API offers an abstraction layer that helps keep Cassandra’s internal storage structure as well as details of implementation buried. Collections natively encoded using native syntaxes as well as other commonly used encodings are included.
Developers are able to communicate with Cassandra through Cassandra’s CQL shell-based interface, called cqlsh. This is in the command line on the node. The prompt cqlsh is used to create keyspaces and tables and data, as well as to make changes to the data as well as insert and query tables and much more.
Comparing CQL with SQL
As I mentioned due to their many similarities developers who have SQL prior experience are likely to quickly get started in CQL.
Similar to SQL, CQL stores data in tables that contain columns and rows. The majority of actions and implementations are exactly similar, for example, retrieving all rows of tables, and the way the permissions as well as resources for entities can be managed. If you’re proficient on SQL statements such as SELECT, UPDATE, INSERT, AND DELETE CQL is a breeze.
There are some distinctions. For instance In SQL any column can be used within the WHERE clause. However, in CQL only those columns specifically defined as primary keys can be utilized as restricting columns. Additionally, every query should include a partition key at a minimum CQL.
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CQL’s most popular data types
CQL is equipped with a range of integrated data formats. Let’s take a look at some of the most important types.
Two data types are available to depict text. Any of the two data types either text or varchar is able to be used to create an UTF-8-character string, which is the more recent popular text standard, which supports interna. To deal with data that is using ASCII formatting, CQL also includes the ASCII type.
Numeric types used in CQL are like those that are found within Java along with other programming languages. They include decimals, integers floating-point numbers, and decimal places.
Types of date and time
CQL offers data types for dates times, date ranges timingstamps, length (in weeks, months or nanoseconds).
Data types for handling geospatial and spatial searches are available. It is possible to search and index latitude and longitude data and shape data, as well as points and shapes.
Types of collection
CQL supports collections, which allows for the storage of multiple values in one column. You can use collections for denormalizing or storing smaller quantities of data, like tags, phone numbers or addresses. Collections aren’t appropriate for data which is expected to expand unbounded like every event for a specific user. In these cases, you should consider a table with clustering columns.
Other CQL types of data
There are a variety of other types of data used to deal with specific situations. For instance, CQL includes the blob type to store the binary data, boolean that can be used to determine either true or false data and counter for the definition of counter columns. CQL also has distinct identifiers.