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Consistency ensures that a transaction can only bring the database from one consistent state to another, preserving database invariants: any data written to the database must be valid according to all defined rules, including constraints, cascades, triggers, and any combination thereof. This prevents database corruption by an illegal transaction.
In database systems, consistency (or correctness) refers to the requirement that any given database transaction must change affected data only in allowed ways. Any data written to the database must be valid according to all defined rules, including constraints, cascades, triggers, and any combination thereof. This does not guarantee correctness ...
The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). The term " schema " refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases ).
Codd's twelve rules [1] are a set of thirteen rules (numbered zero to twelve) proposed by Edgar F. Codd, a pioneer of the relational model for databases, designed to define what is required from a database management system in order for it to be considered relational, i.e., a relational database management system (RDBMS).
Beginning MySQL Database Design and Optimization Hardcover Chad Russell American 49.99 520 Thick Apress USA 1 Tutorial Beginning MySQL Database Design and Optimization E-book Chad Russell American 22.34 520 Thick Apress USA 1 Tutorial The Relational Model for Database Management: Version 2 E-book E.F.Codd British 13.88 538 Thick Addison-Wesley USA
A relational database contains multiple tables, each similar to the one in the "flat" database model. One of the strengths of the relational model is that, in principle, any value occurring in two different records (belonging to the same table or to different tables), implies a relationship among those two records.
Database constraints are constraints on a database that require relation to satisfy certain properties. Relations that satisfy all such constraints are legal relations. Pages in category "Database constraints"
A key constraint applies to the set of tuples in a table at any given point in time. A key is not necessarily a unique identifier across the population of all possible instances of tuples that could be stored in a table but it does imply a data integrity rule that duplicates should not be allowed in the database table.