11.5. Summary
Conceptual schemas are normally implemented by mapping them to a logical schema (e.g., relational), refining this, and then generating internal and external schemas (including access rights). Updates and queries may then be performed on the databases and schema(s).
A relational (database) schema is a set of table definitions (stored base tables or derived views), constraints, and derivation rules. A table scheme is a named set of attributes (columns) that draw their values from domains. Each column, or column set, spanned by a minimal uniqueness constraint is a candidate key. Keys are underlined. Each table row is identified by its primary key (doubly underlined if another key exists). The entity integrity rule requires primary ...
Get Information Modeling and Relational Databases, 2nd Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
