cassandra cqlsh 和 python客户端

Keyspaces

A cluster is a container for keyspaces. A keyspace is the outermost container for data in Cassandra, corresponding closely to a schema in a relational database. The keyspace can include operational elements, such as replication factor and data center awareness. Let's create a keyspace:

-- create a keyspace 'my_keyspace'
create keyspace my_keyspace with replication={'class':'SimpleStrategy', 'replication_factor':1};

-- use the keyspace
use my_keyspace;

-- drop the keyspace
drop keyspace my_keyspace;

Creating a table

To create a table type the following in cqlsh, note that you must first create a keyspace and then use that keyspace:

CREATE TABLE users (
 firstname text, 
 lastname text, 
 age int, 
 email text, 
 city text, 
 PRIMARY KEY (lastname)
);

Describe a table

To see detail information about a table type:

DESCRIBE TABLE users;

Insert records

To insert records in the table type:

INSERT INTO users (firstname, lastname, age, email, city) VALUES ('John', 'Smith', 46, 'johnsmith@email.com', 'Sacramento'); 
INSERT INTO users (firstname, lastname, age, email, city) VALUES ('Jane', 'Doe', 36, 'janedoe@email.com', 'Beverly Hills'); 
INSERT INTO users (firstname, lastname, age, email, city) VALUES ('Rob', 'Byrne', 24, 'robbyrne@email.com', 'San Diego');

Querying a table

To query a table type the following:

SELECT * FROM users;

 lastname | age | city          | email               | firstname
----------+-----+---------------+---------------------+-----------
      Doe |  36 | Beverly Hills |   janedoe@email.com |      Jane
    Byrne |  24 |     San Diego |  robbyrne@email.com |       Rob
    Smith |  46 |    Sacramento | johnsmith@email.com |      John

(3 rows)

We can filter the result by using a predicate:

SELECT * FROM users WHERE lastname= 'Doe';

 lastname | age | city          | email             | firstname
----------+-----+---------------+-------------------+-----------
      Doe |  36 | Beverly Hills | janedoe@email.com |      Jane

(1 rows)

Updating records

To update a record in a table type the following:

UPDATE users SET city= 'San Jose' WHERE lastname= 'Doe';

The update should be available almost instantly (remember that cassandra is eventually consistent):

SELECT * FROM users where lastname= 'Doe';

 lastname | age | city     | email             | firstname
----------+-----+----------+-------------------+-----------
      Doe |  36 | San Jose | janedoe@email.com |      Jane

(1 rows)

Deleting records

To delete a record type:

DELETE from users WHERE lastname = 'Doe';

which should result in:

SELECT * FROM users where lastname= 'Doe';

 lastname | age | city | email | firstname
----------+-----+------+-------+-----------

(0 rows)

SELECT * from users;

 lastname | age | city       | email               | firstname
----------+-----+------------+---------------------+-----------
    Byrne |  24 |  San Diego |  robbyrne@email.com |       Rob
    Smith |  46 | Sacramento | johnsmith@email.com |      John

(2 rows)

python cassandra客户端操作：

from cassandra.cluster import Cluster
cluster = Cluster(["10.178.204.225"])
session = cluster.connect('my_keyspace')
session.execute("""
insert into users (lastname, age, city, email, firstname) values ('Jones', 35, 'Austin', 'bob@example.com', 'Bob')
""")
result = session.execute("select * from users where lastname='Jones' ")[0]
print result.firstname, result.age

session.execute("update users set age = 36 where lastname = 'Jones'")
result = session.execute("select * from users where lastname='Jones' ")[0]
print result.firstname, result.age


session.execute("delete from users where lastname = 'Jones'")
result = session.execute("select * from users")
for x in result:
    print x.age

 

参考：

https://academy.datastax.com/resources/getting-started-apache-cassandra-and-python-part-i?unit=getting-started-apache-cassandra-and-python-part-i

https://github.com/dnvriend/apache-cassandra-test/blob/master/readme.md