DBMS - (8) Introduction to SQL

DBMS - (8) Introduction to SQL

SQL의  특성

• SQL or 'sequel'
• Supported by all major commercial database systems.
• Standardized - many new features over time
• Interactive via GUI or prompt, or embedded in programs.
• Declarative, based on relational algebra

query optimizer
- It takes a query written in a SQL language.
- It figures out the best way, the fastest way to execute that on the database

DDL(Data Definition Language)
- Create table, Drop table

DML(Data Management Language)
- query and mofidy databases
- select, insert, delete, update

ohter commands
- indexes, constraints, views, triggers, transactions, authorization

 

The Basic SELECT Statement
- 1,2,3 순서로 어떤 SQL을 작성 할지 생각하면 된다.
select A1,A2,...,An (3) what to return
from R1,R2,...,Rm (1) relations
where condition (2) combine filter

Relational algebra of SELECT
- π(A1,A2,...,An)σ(condition)(R1XR2,...,XRm)

Reference
https://www.youtube.com/watch?v=wxFmiRwXcQY&list=PL6hGtHedy2Z4EkgY76QOcueU8lAC4o6c3&index=11