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database relational database rdbms data independance physical data independance logical data independance codds rules database fundamentals relationships attribute tuple alternate key super key foreign key candidate key primary key keys relationa-database-model erd entity-relationship-diagram er diagram er model relational model data models dbms gzip performance web application design 4nf bcnf 3nf 2nf 1nf normal forms insert update delete anomalies decomposition functional dependency normalization commit rollback grant revoke sql commands dml ddl crud operations delete update insert create table structured query language sql durablity isolation consistancy atomicity transaction acid properties database performance