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What is a view in SQL? When can views be updated?
A view is a virtual table which consists of columns from one or more tables. Through it is same to a table; it is stored in the database. It is a query stored as an object. Therefore, a view is an object in that derives its data from one or more tables. These tables are referred to as base or underlying tables.
Views can be updated if they are described on a single table without any aggregate functions could be mapped to an update on the underlying base table under certain conditions.
Multiple column Queries: Syntax: SELECT COLUMN1, COL2,...... FROM TABLE WHERE (COLUMN1, COL2, ...) IN (SELECT COLUMN1, COL2,.... FROM TABLE WHERE );
What is an entity relationship model? The entity relationship model is a set of basic objects known as entities and relationship between those objects. An entity is a thing or
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 colu
Explain sorted File with advantages? Sorted file The sort utility shall perform one of the subsequent functions: 1.Sort lines of all the named files together and write the
atient(PNumber, Name, NHS_no, Amount_due, DNO, Doctor, Medical_Treatment), relation of schema Staff(StaffNum, Name, DNO, Task) and relation of schema Dept(DNO, Name, Location, Dire
What is a Transaction? A transaction is an event which happens on the database. Generally a transaction reads a value from the database or writes a value to the database. If y
Increased overheads on update : On the drawbacks side, it will need the system to ensure that all replicas of a relation are consistent. This shows that all the replicas of the rel
Difference between Operating System and Database Security Security within the operating system can be executed at various levels ranging from passwords for access to system, t
Problem 1 Why are the operational system keys not recommended for forming data warehouse primary keys? Give any two examples 2 Explain the following performance tuning techn
What is the use of keyword ISA? The use of keyword ISA is to show that a class is a specialization of another class.
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