Populating and Modifying Tables

History

Types

• Hierarchical database system
  • Single-parent hierarchy (Tree structures)
  • Multi-parent hierarchy (Network database system)
• Tables (Relational system)

Key

• Primary key
  • Natural key (straight from tables)
  • Surrogate key (created for key purposes)
• Foreign key (appear as unique identifier)

<aside> 💡 The process of refining a database design to ensure that each independent piece of information is in only one place (except for foreign keys) is known as normalization.

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Result set: Another name for a nonpersistent table, generally the result of an SQL query

Statement Classes

• SQL schema statements (define the data strtuctures)
• SQL data statements (manipulate the data structures)
• SQL transaction statements (begin, end, and roll back transactions)

<aside> 💡 Most SQL implementations treat any text between the /* and */ tags as comments.

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SQL Data Types