Database Management Systems

Big Data and Database Models

• The rise of the internet in the 1990s generated big data, characterized by unprecedented data volumes and rapidly changing data structures.
• Alternative database models and systems optimized for big data have appeared since 2000.
• Relational databases have gradually improved support for big data and continue to dominate the commercial database market.

Database Models

• Hierarchical database model: uses a tree-like structure to organize data.
• Network database model: uses a graph structure to organize data.
• Linked list database model: uses a series of linked records to organize data.
• Relational database model: uses tables with rows and columns to organize data.
• Object-oriented database model: uses objects and classes to organize data.
• Graph database model: uses vertices and edges to organize data.
• Document-oriented database model: uses self-describing data structures such as XML and JSON.

Relational Database Rules

• Relational rules govern tables, including:
  • Exactly one value per cell.
  • Unknown data is represented with a special NULL value.
  • No duplicate column names.
  • No duplicate rows.
  • No row order.

Data Types

• INT or INTEGER: represents integer values.
• VARCHAR(N): represents values with 0 to N characters.
• DATE: represents date values.
• DECIMAL(M, D): represents numeric values with M digits, of which D digits follow the decimal point.
• Other data types include:
  • Spatial data types: store geometric information, such as lines, polygons, and map coordinates.
  • Binary data types: store data exactly as it appears in memory or computer files, bit for bit.

SQL Statements

• CREATE TABLE statement: creates a new table with specified columns and data types.
• DROP TABLE statement: deletes a table, along with all its rows, from a database.