小知识，大挑战！本文正在参与“程序员必备小知识”创作活动。
一、Cassandra介绍
Cassandra是一个混合型的非关系的数据库，类似于Google的BigTable。其主要功能比Dynamo （分布式的Key-Value存储系统）更丰富，但支持度却不如文档存储MongoDB（介于关系数据库和非关系数据库之间的开源产品，是非关系数据库当中功能最丰富，最像关系数据库的。支持的数据结构非常松散，是类似json的bjson格式，因此可以存储比较复杂的数据类型）。
二、下载Cassandra
到官网下载www.apache.org/dyn/closer.…
[root@localhost hbk] wget mirrors.hust.edu.cn/apache/cass…
解压
[root@localhost hbk]# tar -zxvf apache-cassandra-3.11.3-bin.tar.gz
[root@localhost hbk]# cd apache-cassandra-3.11.3
[root@localhost apache-cassandra-3.11.3]# ls
bin CASSANDRA-14092.txt CHANGES.txt conf doc interface javadoc lib LICENSE.txt NEWS.txt NOTICE.txt pylib tools
三、启动服务端
[root@localhost apache-cassandra-3.11.3]# cd bin/
[root@localhost bin]# ./cassandra -R
四、启用CQL
[root@localhost bin]# ./cqlsh
Connected to Test Cluster at 127.0.0.1:9042.
[cqlsh 5.0.1 | Cassandra 3.11.3 | CQL spec 3.4.4 | Native protocol v4]
Use HELP for help.
cqlsh> help;
Documented shell commands:
===========================
CAPTURE CLS COPY DESCRIBE EXPAND LOGIN SERIAL SOURCE UNICODE
CLEAR CONSISTENCY DESC EXIT HELP PAGING SHOW TRACING
CQL help topics:
================
AGGREGATES CREATEKEYSPACE DROPTRIGGER TEXT
ALTERKEYSPACE CREATEMATERIALIZEDVIEW DROPTYPE TIME
ALTERMATERIALIZEDVIEW CREATEROLE DROPUSER TIMESTAMP
ALTERTABLE CREATETABLE FUNCTIONS TRUNCATE
ALTERTYPE CREATETRIGGER GRANT TYPES
ALTERUSER CREATETYPE INSERT UPDATE
APPLY CREATEUSER INSERTJSON USE
ASCII DATE INT UUID
BATCH DELETE JSON
BEGIN DROP_AGGREGATE KEYWORDS
BLOB DROP_COLUMNFAMILY LIST_PERMISSIONS
BOOLEAN DROP_FUNCTION LIST_ROLES
COUNTER DROP_INDEX LIST_USERS
CREATE_AGGREGATE DROP_KEYSPACE PERMISSIONS
CREATE_COLUMNFAMILY DROPMATERIALIZEDVIEW REVOKE
CREATEFUNCTION DROPROLE SELECT
CREATEINDEX DROPTABLE SELECT_JSON
五、相关操作
1、建立keyspace
cqlsh:hbk_space> CREATE KEYSPACE "hbk_space" WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 3} AND durable_writes = 'true';
cqlsh:hbk_space> DESCRIBE KEYSPACES
system_schema system_auth system system_distributed system_traces hbk_space
cqlsh:hbk_space> USE hbk_space ;
cqlsh:hbk_space> CREATE TABLE hbk_table(id int PRIMARY KEY ,name text ,age int,phone varint );
cqlsh:hbk_space> select * from hbk_table ;
id | age | name | phone
----+-----+------+-------
(0 rows)
cqlsh:hbk_space> ALTER TABLE hbk_table ADD emp_address varchar ;
cqlsh:hbk_space> DESCRIBE TABLE hbk_table ;
CREATE TABLE hbk_space.hbk_table (
id int PRIMARY KEY,
age int,
emp_address text,
name text,
phone varint
) WITH bloom_filter_fp_chance = 0.01
AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
AND comment = ''
AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}
AND compression = {'chunk_length_in_kb': '64', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}
AND crc_check_chance = 1.0
AND dclocal_read_repair_chance = 0.1
AND default_time_to_live = 0
AND gc_grace_seconds = 864000
AND max_index_interval = 2048
AND memtable_flush_period_in_ms = 0
AND min_index_interval = 128
AND read_repair_chance = 0.0
AND speculative_retry = '99PERCENTILE';
cqlsh:hbk_space> insert into hbk_table (id,age, emp_address , name , phone ) values(1,20,'nankang','hbk',18679758769);
cqlsh:hbk_space> select * from hbk_table ;
id | age | emp_address | name | phone
----+-----+-------------+------+-------------
1 | 20 | nankang | hbk | 18679758769
(1 rows)
cqlsh:hbk_space> UPDATE hbk_table set emp_address = 'ganzhou' where id=1;
cqlsh:hbk_space> select * from hbk_table ;
id | age | emp_address | name | phone
----+-----+-------------+------+-------------
1 | 20 | ganzhou | hbk | 18679758769
(1 rows)
cqlsh:hbk_space> DELETE from hbk_table where id=1;
cqlsh:hbk_space> select * from hbk_table ;
id | age | emp_address | name | phone
----+-----+-------------+------+-------
