1. Why use Nosql

Explosive growth of users' personal information, social networks, geographic locations, user-generated data, user logs, and more!
At this time, we need to use Nosql database, Nosql can handle the above situation very well!

2. What is Nosql

Nosql = Not Only SQL
Relational database: table, row, column
Generally refers to non-relational database
Many data types User's personal information, social network, geographic location, these data typesThe storage does not need a fixed format!It can be scaled horizontally without extra operations!Map uses key-value pairs to control!

3. Features of Nosql

Decoupling!
1. Easy to expand (there is no relationship between data, it is easy to expand!)
2. Large data volume and high performance (Redis writes 80,000 times per second and reads 110,000)
3. Data typeis diversity!(No need to design the database in advance! Take it as you go)
4. The difference between traditional RDBMS and Nosql
(1) Traditional RDBMS:
Structured Organization
SQL
Data and RelationshipsAll exist in separate tables (rows, columns)
Data Manipulation Language, Data Definition Language
Strictly Consistency
Basic Transaction
(2) Nosql
Not Just Data
> No fixed query language
Key-value store, column store, document store, graph database (social relationship)
Eventual consistency
CAP theorem and BASE
High performance, high scalability, high performanceAvailable

4. 3V+3 high (understand)

3Vs in the era of big data: mainly describe problems
Massive, diverse, real-time
3 highs in the era of big data: mainly the requirements for programs
High concurrency, high scalability, high performance

5. Four major categories of Nosql

1. KV key-value pair
2. Document database
MongoDB: is a database based on distributed file storage, written in c++, mainly used to process a large number of documents!
3. Column store database
HBase
Distributed file system
4. Graph relational database
It does not store graphs, but relations.For example: circle of friends social network, advertising recommendation.