Using Java to Implement Apache Cassandra Aggregated Queries

Implementing various aggregation queries for Apache Cassandra using Java can be accomplished through the following steps: 1. Configure Cassandra connection: Firstly, it is necessary to import Cassandra's Java driver and related dependencies. Add the following dependencies to the pom.xml file in Maven: <dependencies> <dependency> <groupId>com.datastax.oss</groupId> <artifactId>java-driver-core</artifactId> <version>4.12.0</version> </dependency> </dependencies> Then, create a Cassandra session and connect to the Cassandra cluster: import com.datastax.oss.driver.api.core.CqlSession; CqlSession session = CqlSession.builder() .withKeyspace("your_keyspace_name") .addContactPoint(new InetSocketAddress("ip_address", 9042)) .build(); Ensure Replace ` your '_ Keyspace_ Name and IP_ Address' is the correct key space name and the IP address of the Cassandra node. 2. Execute query: You can use CQL queries to perform various data aggregation operations. Here are some common examples of aggregation queries and their corresponding Java code implementations: -Accumulated total query: import com.datastax.oss.driver.api.core.CqlSession; import com.datastax.oss.driver.api.core.cql.Row; import com.datastax.oss.driver.api.core.cql.SimpleStatement; import com.datastax.oss.driver.api.core.cql.ResultSet; CqlSession session=//Create Cassandra session SimpleStatement stmt = SimpleStatement.newInstance("SELECT COUNT(*) FROM your_table_name"); ResultSet rs = session.execute(stmt); Row row = rs.one(); long count = row.getLong(0); System.out.println("Total count: " + count); Ensure that the 'your'_ Table_ Replace 'name' with the name of the table to be queried. -Average Query: import com.datastax.oss.driver.api.core.CqlSession; import com.datastax.oss.driver.api.core.cql.Row; import com.datastax.oss.driver.api.core.cql.SimpleStatement; import com.datastax.oss.driver.api.core.cql.ResultSet; CqlSession session=//Create Cassandra session SimpleStatement stmt = SimpleStatement.newInstance("SELECT AVG(column_name) FROM your_table_name"); ResultSet rs = session.execute(stmt); Row row = rs.one(); double avg = row.getDouble(0); System.out.println("Average: " + avg); Ensure that the 'column'_ Replace 'name' with the name of the column for which you want to calculate the average. -Maximum value query: import com.datastax.oss.driver.api.core.CqlSession; import com.datastax.oss.driver.api.core.cql.Row; import com.datastax.oss.driver.api.core.cql.SimpleStatement; import com.datastax.oss.driver.api.core.cql.ResultSet; CqlSession session=//Create Cassandra session SimpleStatement stmt = SimpleStatement.newInstance("SELECT MAX(column_name) FROM your_table_name"); ResultSet rs = session.execute(stmt); Row row = rs.one(); int max = row.getInt(0); System.out.println("Max: " + max); Ensure that the 'column'_ Replace 'name' with the name of the column for which you want to find the maximum value. -Grouping aggregation query: import com.datastax.oss.driver.api.core.CqlSession; import com.datastax.oss.driver.api.core.cql.Row; import com.datastax.oss.driver.api.core.cql.SimpleStatement; import com.datastax.oss.driver.api.core.cql.ResultSet; CqlSession session=//Create Cassandra session SimpleStatement stmt = SimpleStatement.newInstance("SELECT column1, COUNT(*) FROM your_table_name GROUP BY column1"); ResultSet rs = session.execute(stmt); for (Row row : rs) { String column1Value = row.getString("column1"); long count = row.getLong("count"); System.out.println(column1Value + ": " + count); } Ensure to replace 'column1' with the name of the column to be grouped. 3. Close Cassandra connection: After executing all the queries, remember to close the Cassandra session: session.close(); The above is the basic example code for implementing various aggregation queries in Apache Cassandra using Java. Please adjust and optimize according to your specific needs.