DBMS Intro.

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Database Management SYstem.

  • table = entity
  • column = attributes / fields

Main Theme of DBMS

  • Abstraction
  • Instance & Schema


Abstractions is a hiding process of irrelevant details. It has three steps

  • Physical level (making environment)
  • Logical level (type)
  • view (UI)


Schema is a design or blueprint of a database .

  • Physical
  • Logical
  • View

database system

  • table = entity
  • columns = attributes
  • rows = tuples


Key uses for relational purpose or accessing unique row .

Primary key

Primary key a set of column which describe unique row.

  • underline

Super Key

Super key is a set of one or more columns which describe unique row.

Candidate key

It is super key which ignore reduntant columns

Alternative key

Alternative key is aliasing process.

Composite key

Composite key is a set of column which describe unique rows.

Foreign key

Foreign key is a coulmn which point another table. You can compare is a passport


  • one to one
  • one to many
  • many to one
  • many to many
  • polymorphic
sql, dbms, database