Cassandra - Create Table

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Creating a Table

You can create a table using the command CREATE TABLE. Given below is the syntax for creating a table.

Syntax

CREATE (TABLE | COLUMNFAMILY) <tablename>
('<column-definition>' , '<column-definition>')
(WITH <option> AND <option>)

Defining a Column

You can define a column as shown below.

column name1 data type,
column name2 data type,

example:

age int,
name text

Primary Key

The primary key is a column that is used to uniquely identify a row. Therefore,defining a primary key is mandatory while creating a table. A primary key is made of one or more columns of a table. You can define a primary key of a table as shown below.

CREATE TABLE tablename(
   column1 name datatype PRIMARYKEY,
   column2 name data type,
   column3 name data type.
   )

or

CREATE TABLE tablename(
   column1 name datatype PRIMARYKEY,
   column2 name data type,
   column3 name data type,
   PRIMARY KEY (column1)
   )

Example

Given below is an example to create a table in Cassandra using cqlsh. Here we are −

  • Using the keyspace howcodex

  • Creating a table named emp

It will have details such as employee name, id, city, salary, and phone number. Employee id is the primary key.

cqlsh> USE howcodex;
cqlsh:howcodex>; CREATE TABLE emp(
   emp_id int PRIMARY KEY,
   emp_name text,
   emp_city text,
   emp_sal varint,
   emp_phone varint
   );

Verification

The select statement will give you the schema. Verify the table using the select statement as shown below.

cqlsh:howcodex> select * from emp;

 emp_id | emp_city | emp_name | emp_phone | emp_sal
--------+----------+----------+-----------+---------

(0 rows)

Here you can observe the table created with the given columns. Since we have deleted the keyspace howcodex, you will not find it in the keyspaces list.

Creating a Table using Java API

You can create a table using the execute() method of Session class. Follow the steps given below to create a table using Java API.

Step1: Create a Cluster Object

First of all, create an instance of the Cluster.builder class of com.datastax.driver.core package as shown below.

//Creating Cluster.Builder object
Cluster.Builder builder1 = Cluster.builder();

Add a contact point (IP address of the node) using the addContactPoint() method of Cluster.Builder object. This method returns Cluster.Builder.

//Adding contact point to the Cluster.Builder object
Cluster.Builder builder2 = build.addContactPoint( "127.0.0.1" );

Using the new builder object, create a cluster object. To do so, you have a method called build() in the Cluster.Builder class. The following code shows how to create a cluster object.

//Building a cluster
Cluster cluster = builder.build();

You can build a cluster object using a single line of code as shown below.

Cluster cluster = Cluster.builder().addContactPoint("127.0.0.1").build();

Step 2: Create a Session Object

Create an instance of Session object using the connect() method of Cluster class as shown below.

Session session = cluster.connect( );

This method creates a new session and initializes it. If you already have a keyspace, you can set it to the existing one by passing the keyspace name in string format to this method as shown below.

Session session = cluster.connect(“ Your keyspace name ” );

Here we are using the keyspace named tp. Therefore, create the session object as shown below.

Session session = cluster.connect(“ tp” );

Step 3: Execute Query

You can execute CQL queries using the execute() method of Session class. Pass the query either in string format or as a Statement class object to the execute() method. Whatever you pass to this method in string format will be executed on the cqlsh.

In the following example, we are creating a table named emp. You have to store the query in a string variable and pass it to the execute() method as shown below.

//Query
String query = "CREATE TABLE emp(emp_id int PRIMARY KEY, "
   + "emp_name text, "
   + "emp_city text, "
   + "emp_sal varint, "
   + "emp_phone varint );";
session.execute(query);

Given below is the complete program to create and use a keyspace in Cassandra using Java API.

import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.Session;

public class Create_Table {

   public static void main(String args[]){

      //Query
      String query = "CREATE TABLE emp(emp_id int PRIMARY KEY, "
         + "emp_name text, "
         + "emp_city text, "
         + "emp_sal varint, "
         + "emp_phone varint );";
		
      //Creating Cluster object
      Cluster cluster = Cluster.builder().addContactPoint("127.0.0.1").build();
   
      //Creating Session object
      Session session = cluster.connect("tp");
 
      //Executing the query
      session.execute(query);
 
      System.out.println("Table created");
   }
}

Save the above program with the class name followed by .java, browse to the location where it is saved. Compile and execute the program as shown below.

$javac Create_Table.java
$java Create_Table

Under normal conditions, it should produce the following output −

Table created
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