Concept of database
SQL
Simple example
create \ insert \ update \ delete\select
WHERE\BETWEEN\IS NULL\LIKE
avg\count\max
group by\order by
Relational Database
Entities: things that exist, including all attributes of things. Entities of the same type are called entity sets.
Attribute: The characteristics of an entity. An entity can be composed of several attributes, and each attribute has a value range.
Relational database composition structure
Big Data
Whoever has the initiative in data will win the future.
Five characteristics of big data: diversity, value, large amount, high speed, and reality.
Hadoop is used for user portrait and network click stream log mining.
NoSQL database
Non-relational database, used for large-scale data storage. It is an important supplement to relational databases.