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In a relation, tuples are not inserted in any definite order. Ordering of tuples is not defined as a part of a relation definition. Though, records may be structured later according to some attribute value in the storage systems. For instance, records in PERSON table may be structured according to PERSON_ID. Such organisation or data depends on the requirement of the underlying database application. Though, for the purpose of display we may get them displayed in the sorted order of age. The following table is sorted by age. It is also worth states here that relational model does not permit duplicate tuples
PERSON
PERSON_ID NAME AGE ADDRESS
2 Sharad Gupta 33 Pocket 2, Mayur Vihar.
1 Sanjay Prasad 35 b-4,Modi Nagar
3 Vibhu Datt 36 c-2, New Delhi
Super Keys, Candidate Keys and Primary Keys for the Relations
As discussed in the last section ordering of relations does not matter and all tuples in a relation are unique. Though, can we uniquely recognize a tuple in a relation? Let us talk about the concepts of keys that are primarily used for the purpose as above.
Log based recovery: Let us first describe the term transaction log in the context of DBMS. A transaction log is a record in DBMS that remains track of all the transactions of a dat
Association as a cache This association must be updated when any new element is added to it, but testing for overlap using association is more efficient. Figure:
Consider the entity type dependent related to employee entity, which is used to keep track of the dependents of every employee. The attributes of dependents are: name, sex, birth d
1) Define a job scheduling strategy that will meet business requirement of reporting availability by 6am CST for the following cubes? Show the job scheduling dependencies in a pict
What is known as clustering file organization? In the clustering file organization, records of several dissimilar relations are stored in the similar file.
Write short notes on Schema diagram. A database schema along with primary key and foreign key dependencies can be depicted pictorially by schema diagram. Every relation appea
How do I use strap on?#
Name the three major set of files on disk that compose a database in Oracle. There are three main sets of files on disk that compose a database. All the files are binary. These
Horizontal Fragmentation- Horizontal fragmentation groups together the tuples in a relation that are collectively used by the main transactions. A horizontal fragment is produced b
Define the basic operations of the relational algebra? Ans: Basic operators of relational algebra are: 1. Union (∪) - Selects tuples which are in either P or Q or in bot
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