sql-2

[woshahua]

sql-2

index

CREATE INDEX  index_name  ON table_name 
[USING method]
(
    column_name [ASC | DESC] [NULLS {FIRST | LAST }],
    ...
);

view

• 通过保存select语句来节省空间。??? select执行，为什么需要view来节省空间。
• 可复用

predict

• like
• between
• is null, is not null
• in
• exists

unique

• UNIQUE 和 PRIMARY KEY 约束均为列或列集合提供了唯一性的保证。

ERD

• 1-1
  • basically, we combine this to a single table.
  • unless one table is accessed frequently, and the other is not.
  • like a golang inherent
• 1-n
  • put foreign key to many table
  • like a tree structure
• n-n
  • add another table to link these two table, n-1-n

check later

• webRTC https://peerjs.com/
• simple css https://github.com/kognise/water.css
• compiler https://kishuagarwal.github.io/life-of-a-binary.html
• implement database with c https://cstack.github.io/db_tutorial/
• python scrapy https://github.com/my8100/files/tree/master/scrapydweb