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Describe Hashing in DBMS?
Hashing: Hashing is a technique to store data within an array so which storing, searching, inserting and deleting data is fast (in theory it's O(1)). For this every record requires an unique key.
The primary idea is not to find for the correct position of a record along with comparisons but to compute the position inside the array. The function which returns the position is known the 'hash function' and the array is called a 'hash table'.
Consider the subsequent relations for a database which keeps track of business trips of salespersons in a sales office: SALESPERSON (SSN, Name, start_year, Dept_no) TRIP (SSN, Fr
Define instance and schema? Instance: Collection of data stored in the data base at a certain moment is Schema: The overall design of the data base is known as the data base
What is conceptual schema? The schemas at the view level are known as subschema that describe dissimilar views of the database.
Mappings between Levels and Data Independence The 3 levels of abstraction in the database do not exist separately of each other. There must be some correspondence, or mapping
Define Partial Key and Primary Key A partial key, also known as discriminator, is the set of attributes which can uniquely identify weak entities that are related to similar o
Explain the Relational Completeness Codd described the term relational completeness to consider to a language that is complete with respect to first-order predicate calculus ex
What is the main difference between read-only and update methods? A read-only method does not affect the values of a variable in an object, whereas an update method may alter t
Q. What is relational algebra and calculus? Explain the relational algebra operators :- Selection and predicate, set operation, joins and division. Sol. Relational Algebra
What is use of generating such tables? How can you create temporary tables? When you require a table only for a short time after that you want it to disappear automatically you
E-R Model This data model is based on real world that consists of basic objects named entities and of relationship among these objects. Entities are illustrated in a database
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