Basic Syntax Examples of GeminiDB Cassandra Instances

This section describes the basic syntax of GeminiDB Cassandra instances.

• Keyspace syntax
  • Create a keyspace.

    Example:

    CREATE KEYSPACE IF NOT EXISTS nosql WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '3'};

    In this example, the keyspace name is set to nosql and class to SimpleStrategy. replication_factor indicates the number of copies. A GeminiDB Cassandra instance provides strong consistency, three-copy storage by default.

  • Run DESC <keyspace_name> to verify the creation results.
    Figure 1 Verifying the creation results
    
  • Run use <keyspace_name> to switch to the created keyspace.
    Figure 2 Switching the keyspace
    
  • Run DROP KEYSPACE <keyspace_name> to delete the created keyspace.
    Figure 3 Deleting the keyspace
    
• Table syntax
  • Create a table.

    Example:

    CREATE TABLE nosql_table(user_id int, age int, user_name text, PRIMARY KEY(user_id));

    nosql_table is a table name defined by the following three columns: user_id, age, and user_name. user_id indicates a user ID of the INT data type. age indicates user age of the INT data type. user_name indicates a username of the TEXT data type. The primary key is user_id.

  • Run DESC <table_name> to verify the creation results.
    Figure 4 Verifying the creation results
    
  • Insert data into the table, for example,

    INSERT INTO nosql_table (user_id, age, user_name) VALUES (1, 10, 'user1');

    INSERT INTO nosql_table (user_id, age, user_name) VALUES (2, 20, 'user2');

    INSERT INTO nosql_table (user_id, age, user_name) VALUES (3, 30, 'user3');

  • Run SELECT * FROM <table_name> to query table data.
    Figure 5 Querying table data
    
  • Add a column to the table, for example:

    ALTER TABLE nosql_table ADD gender text;

  • Update data in a table of a keyspace, for example:

    UPDATE nosql.nosql_table SET gender = 'male' WHERE user_id = 1;

    UPDATE nosql.nosql_table SET gender = 'male' WHERE user_id = 2;

    UPDATE nosql.nosql_table SET gender = 'female' WHERE user_id = 3;

    Figure 6 Viewing the update results
    
  • Delete data from a table in a keyspace, for example:

    Delete age data of the user whose ID is 1.

    DELETE age FROM nosql.nosql_table WHERE user_id=1;

    Figure 7 Deleting a data record
    

    Delete the entire record of the user whose ID is 2.

    DELETE FROM nosql.nosql_table WHERE user_id=2;

    Figure 8 Deleting the entire record
    
  • Delete an entire table, for example:

    DROP TABLE nosql.nosql_table;

    Figure 9 Deleting an entire table
    
• HELP command
  • Run HELP to view all supported commands.
    Figure 10 Viewing all supported commands
    
  • Run HELP <COMMAND> to query the usage of a command.

    Example: HELP DESC