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A super key is an attribute or set of attributes used to recognize the records uniquely in a relation.
For instance, in the Relation PERSON defines earlier PERSON_ID is a super key since PERSON_ID is unique for every person. Likewise (PERSON_ID, AGE) and (PERSON_ID, NAME) are also super keys of the relation PERSON as their combination is also unique for each record.
Before we talk about the relational model in more detail, let us first define some very basic terms used in this model. Tuple Every row in a table shows a record and is cal
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
Given the following set of functional dependencies {cf?bg, g?d, cdg?f, b?de, d?c} defined on R(b,c,d,e,f,g) a.Find a non-redundant cover. b.Find a canonical cover.
User error : This contains errors in the program (e.g., Logical errors) with errors made by online users of database. These types of errors can be avoided by applying some check
What are the advantages of by using an index and what are its disadvantages ? In difference, if the search key of a secondary index is not a candidate key, it is not sufficient
Before defines the second type of integrity constraint, viz., Entity Integrity, we should be well-known with the concept of NULL. Mostly, NULL is intended as a basis for dealing
Partial Key : It is a group of attributes that can uniquely identify small entities and that are related to same base entity. It is sometime named as Discriminator. Altern
Using your cache simulator and using smalltex.din as your memory trace determine the total miss rate, compulsory miss rate, capacity miss rate, and conflict miss rate for the follo
How can you map NULL values to other values while display? IF( ) , IFNULL( ) keywords are used to do so. They are 'LIMIT' is used for the following kinds of problems: 1) Ans
what is the need of a log in dbms
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