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What is a foreign key, and what is it used for?
A foreign key is used to establish relationships between relations in the relational model. Technically, a foreign key is a column (or columns) appearing in one relation that is (are) the primary key of another table. Although there might be exceptions, the values in the foreign key columns usually must correspond to values existing in the set of primary key values. This correspondence necessity is created in a database using a referential integrity constraint on the foreign key.
How does Tuple-oriented relational calculus vary from domain-oriented relational calculus? The tuple-oriented calculus uses a tuple variables i.e., variable whose only allowed
Domain Constraints Domain constraints are primarily formed for defining the logically correct values for an attribute of a relation. The relation allows attributes of a relatio
distributed quey processing
describe all the tables you have created. ?get table_name, status, num_rows, user_stats in user_tables system view ?get table_name, constraint_name, constraint_type in user_constr
WHY SHOULD NULL IN A RELATION BE AVOID AS possible?
What is transaction? Transaction is a unit of program implementation that accesses and possibly updated several data items.
Define the Traditional System Analysis and Design Traditional System Analysis and Design (SAD) have three basic life cycle models. A typical software lifecycle consists of the
Define what Immediate database modification technique uses? Ans: Both undo and redo.
Explain what is Aggregation ? Aggregation: This is used whenever we intend to show a relationship between an entity and the relationship. There is no provision for this in th
While sorting, if the main storage available is not enough, the system writes data to an external help file. The SAP profile parameter, which determines DIR_SORTTMP
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