Keyphrases
- foreign key
- relational databases
- integrity constraints
- databases
- query optimization
- relational schema
- regular expressions
- functional dependencies
- relational model
- queries involving
- primary key
- join queries
- conjunctive queries
- null values
- spatial databases
- xml data
- data model
- database
- query answering
- relational data
- xml schema
- data integration
- efficient processing
- query language
- query processing