executecql

Using an Apache® Cassandra® database C++ interface, create a Cassandra® database connection and execute a CQL query to import data from a Cassandra database table into MATLAB®. In this case, the Cassandra database contains the employees_by_job database table with employee data in the employeedata keyspace.

Create a Cassandra database connection using the configured data source CassandraDataSource and a blank user name and password. The apacheCassandra function returns conn as a connection object.

datasource = "CassandraDataSource";
username = "";
password = "";
conn = apacheCassandra(datasource,username,password);

Write a CQL query that selects all employees who are programmers or shop clerks hired before April 30, 2006, and retrieves their job identifiers, hire dates, and email addresses. job_id is the partition key of the employees_by_job database table, and hire_date is a clustering column.

query = strcat("SELECT job_id,hire_date,email ", ... 
    "FROM employeedata.employees_by_job ", ...
    "WHERE job_id IN ('IT_PROG','SH_CLERK') ", ...
    "AND hire_date < '2006-04-30';");

Execute the CQL query and display the first few rows of results.

results = executecql(conn,query);
head(results)

ans=8×3 table
      job_id       hire_date       email   
    __________    ___________    __________

    "IT_PROG"     05-Feb-2006    "VPATABAL"
    "IT_PROG"     03-Jan-2006    "AHUNOLD" 
    "IT_PROG"     25-Jun-2005    "DAUSTIN" 
    "SH_CLERK"    24-Apr-2006    "AWALSH"  
    "SH_CLERK"    23-Feb-2006    "JFLEAUR" 
    "SH_CLERK"    24-Jan-2006    "WTAYLOR" 
    "SH_CLERK"    13-Aug-2005    "JDILLY"  
    "SH_CLERK"    14-Jun-2005    "KCHUNG"  

results is a table with the job_id, hire_date, and email variables. The hire_date variable is a datetime array and the job_id and email variables are string arrays.

Close the Cassandra database connection.

close(conn)

Using the Apache® Cassandra® database C++ interface, create a Cassandra database connection and execute a CQL query to import data from a Cassandra database table into MATLAB®. Specify a consistency level for returning query results. In this case, the Cassandra database contains the employees_by_job database table with employee data in the employeedata keyspace.

Create a Cassandra database connection using the configured data source CassandraDataSource and a blank user name and password. The apacheCassandra function returns conn as a connection object.

datasource = "CassandraDataSource";
username = "";
password = "";
conn = apacheCassandra(datasource,username,password);

Write a CQL query that selects all employees who are programmers and retrieves their hire dates and email addresses. job_id is the partition key of the employees_by_job database table. Limit the returned data to three rows.

query = strcat("SELECT hire_date,email ", ... 
    "FROM employeedata.employees_by_job ", ...
    "WHERE job_id = 'IT_PROG'", ...
    "LIMIT 3;");

Execute the CQL query with the consistency level set to one node and display the results.

level = "ONE";
results = executecql(conn,query,'ConsistencyLevel',level)

results=3×2 table
     hire_date       email   
    ___________    __________

    21-May-2007    "BERNST"  
    07-Feb-2007    "DLORENTZ"
    05-Feb-2006    "VPATABAL"

In this case, only one replica node responds with returned data. results is a table with the hire_date and email variables. The hire_date variable is a datetime array and the email variable is a string array.

Close the Cassandra database connection.

close(conn)