Cassandra 2.1 data query syntax.

1, Official document, basic typedata Query Language documentation:http://www.datastax.com/documentation/cql/3.1/cql/cql_reference/update_r.html

data types supported by CQL:Compared to MySQL, there are several types of interesting,uuid type, map,list,set type, this optimization association query, directly to the list into a record.

CQL Type	Constants	Description
Ascii	Strings	Us-ascii character string
bigint	Integers	64-bit signed Long
Blob	BLOBs	Arbitrary bytes (no validation), expressed as hexadecimal
Boolean	Booleans	True or False
Counter	Integers	Distributed counter Value (64-bit long)
Decimal	integers, floats	Variable-precision Decimal Java type
Double	Integers	64-bit IEEE-754 floating point Java type
Float	integers, floats	32-bit IEEE-754 floating point Java type
inet	Strings	IP address string in IPV4 or IPV6 format, used by the PYTHON-CQL driver and CQL native protocols
Int	Integers	32-bit signed integer
List	N/A	A collection of one or more ordered elements
Map	N/A	A Json-style Array of literals: {literal:literal, literal:literal ...}
Set	N/A	A collection of one or more elements
Text	Strings	UTF-8 encoded string
Timestamp	Integers, strings	Date plus time, encoded as 8 bytes since epoch
Timeuuid	UUIDs	Type 1 UUID only
Tuple	N/A	Cassandra 2.1 and later. A Group of 2-3 fields.
Uuid	UUIDs	A uuid in the standard UUID format
varchar	Strings	UTF-8 encoded string
Varint	Integers	Arbitrary-precision integer Java type

data types supported by Java:

CQL type	java type
decimal
float
double
varint

In this topic:

• Blob type
  
• Collection type
  
• Counter type
  
• UUID and Timeuuid types
  
• UUID and TIMEUUID functions
  
• Timestamp type
  
• Tuple type
  
• user-defined type

2, view, create keyspace, data sheetThe View command is similar to MySQL.

Desc cluster;desc keyspaces;desc keyspace portfoliodemo;desc tables;desc table stocks;

Create Keyspace: Default to make Simplestrategy copy type.

Create a keyspace.cqlsh> Create Keyspace demodb with REPLICATION = {' class ': ' Simplestrategy ', ' replication_factor ': 1} and durable_writes = true; Use the keyspace.cqlsh> use Demodb;

To create a data table:

CREATE TABLE users (userid uuid PRIMARY KEY, first_name text, last_name text, emails set<text>, Top_scores lis T<int>, Todo Map<timestamp, text>, create_time timestamp);

Cassandra has a feature is the bottom of the distributed, so the query sort of time limit is more.to create a time flashback query according to the user, you must write the table again when you create it.

CREATE TABLE users (  userid uuid PRIMARY KEY,  first_name text,  last_name text,  emails set<text>,< C7/>top_scores list<int>,  todo Map<timestamp, text>,  create_time timestamp  PRIMARY KEY ( UserID, Create_time)) with Clustering ORDER by (Create_time DESC);

The default definition of the time sequence, flashbacks need to be redefined, and put this field into the primary key.Reference: Http://www.datastax.com/documentation/cql/3.1/cql/cql_reference/refClstrOrdr.html
The Update table structure is similar to MySQL:

Alter TABLE users alter bio TYPE text;

3, inserting data, updatingsimilar to MYSQ: where emails is a set type.

INSERT into Users (userid, first_name, last_name, emails)  VALUES (cfd66ccc-d857-4e90-b1e5-df98a3d40cd6, ' Frodo ', ' Baggins ', {' [email protected] ', ' [email protected] '};

Update data to compare special time List,map,set types:other similar, refer to http://www.datastax.com/documentation/cql/3.1/cql/cql_reference/update_r.html

Add emails data: Use + UPDATE users SET emails = emails + {' [email protected] '} WHERE userid = cfd66ccc-d857-4e90-b1e5-df98a3d40cd 6. Delete emails data: Use-UPDATE users SET emails = emails-{' [email protected] '} WHERE userid = Cfd66ccc-d857-4e90-b1e5-df98a3d40 cd6; empty emails data: use {} UPDATE users SET emails = {} WHERE userid = Cfd66ccc-d857-4e90-b1e5-df98a3d40cd6;

4. Querying data

Number of Queries Select COUNT (*) from users; query Top 10 SELECT * from users LIMIT, allow FILTERING; query by token select * from users WHERE token (userid) >= token (CFD66CCC-D857-4E90-B1E5-DF98A3D40CD6); Check token content, token can only be primary key. SELECT TOKEN (userid) from the Users WHERE token (userid) >= token (CFD66CCC-D857-4E90-B1E5-DF98A3D40CD6);

It also supports queries such as distinct,in, but does not support associated queries, after all, it is not a relational database.

Cassandra 2.1 data query syntax.