data warehouse

Catalog

How does data warehouse come into being

Define data warehouse

Characteristics of data warehouse

Understand structured

---

How does data warehouse come into being

Q： We all know , Each application has its own database , Save the data to the database , If you want to analyze the data , Why can't you directly retrieve data from the database for analysis ？

A：On-Line Transaction Processing On line transaction processing The process (OLTP) yes Business oriented , From the front desk 、 application 、 The database works together , The input data can be processed instantly , Answer in time . But it's not suitable for OLTP To read data from the database for analysis , For the operation Library , The pressure of reading is greater than that of writing , And it will occupy the business processing of the database , stay OLTP In the environment , database Store only new data for weeks or months , Cannot store too old data , So this is not conducive to data analysis , So for Both meet the data analysis , Without affecting business , So there is data warehouse .

Define data warehouse

Data warehouse is a system for storing , analysis , Reporting data system , Build an integrated data environment for analysis , The results of the analysis provide decision support for enterprises , The data warehouse itself does not produce any data , Data comes from different external systems , At the same time, the data warehouse does not need to consume any data , The results are open to various external applications . We put this analysis oriented , The system that supports analysis is called OLAP（ On line analytical processing ）, The data warehouse is OLAP An implementation of the system .

Characteristics of data warehouse

• subject-oriented

• Integration

• non-volatile

• Time varying

Understand structured

Q： When operating data warehouse , It uses SQL Structured query language , So in structured query language structured What does that mean? ？

A： Structured query language query highlights that the data queried is structured data , Structured data is relative to unstructured data , Structured data refers to the data logically expressed and realized by two-dimensional table structure , Store and manage through relational database , Unstructured data has XML,HTML wait , The essence is that the data format in different files is different .