DOM
1. JavaScript 위치
2. DOM tree (header, footer, section, aside)
browser와 user communication 하는 방법
DOM = Document Object Model=> webpage HTML
=====
What is Database?
- A database generally reffers to a structured collectio of structured information or data stored electronically in a computer system. The database is usually controlled by a database......
// need to add additional information
for web developer's perspective... used for web system (DB)
website-> starbucks-> click on the selected drink -> detailed description-> web system, data is sourced from the database.
** information are all saved in a database, saved in the system for long period of time.
This is called three-tiered web system
web client
like(chrome, safari) request ->
web application server
request (detailed information from the database) ->
DBMS software = software data
database = actual hardware data
front-end use web client-> web application server, easier for front-end developers,
back-end use api database server, database (raw data)
DBMS (Database Management System) is a software
보존 (saved) hard disk, usb, permanantly saved, data saved 체계적 관리
DMS 사용하는 이유:
생산성-read, create, delete, update
기능성- advanced search, 대용량 데이터 저장, fast speed, 기능확장의 유여함
신뢰성-scalability,load balancing, data retrieved, data restore
What is 관계형 vs. 비관계형 database?
관계형 database (RDBMS) (relational database)
-
looks like a excel sheet full of data
column (id,book title, author, publisher, price)
row (id - holds the numbering in order for primary key) -
not related database
When do you use it?
What is table, column, row?
column id - name - id - identification number - user_id
row -
관계형 table database is as below:
One to One, (Name, id) are PK (primary key)
users -> identification numbers (A to B) in 1:1 ratio in two tables.
column (1) : column (1)
One to Many, (users - pets)
1:2 table ratio
one owner can own 2 pets
foreign key is still used
reference pet table -> user id column table -> id(pk)
Many to Many (2+ more authors per column),
... but problem occurs (titles overlap),
the titles with the same title can be two different stories.
author -> author_books -> books
need to create another table,
a separte table with author_id / book_id is added
to make sure there is no overlapping in data
books are usually use foreign keys
Primary Key vs. Foreign Key
ACID (Atomicity, Consistency, Isolation, Durability):
Atomicity-
Consistency-
Isloation-
Durablitiy-
Transaction:
bank system -> from sender -> bank takes out money -> to recipient receives money-> rollback can occur when something is missed...
MySQL:
Database를 지시하기 위해서 programming:
DDL - Data Define Language
** defines the language of the data,
DML - Data Manipulation Language
** insert, update, delete
DQL- Data Query Language
** select , 불러온는 데이터 by using query
where,
like,
inner join - table1 and table2
