Get latest, qualitative and comprehensive notes of database concept it 802 class 12. it covers all topics very optimally that certainly help students to secure high marks. What is data? Generally, data is collection of characters, numbers and other symbols that represents values of some situations or variables. It is raw facts which have not […]
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(a) Can they insert the following tuples to the UNIFORM Relation? Give reasons in support of your answer.(i) 7, Handkerchief, NULLAns: Yes, it can be inserted as UColor does not have Not Null constraint.(ii) 4, Ribbon, RedAns: No, it cannot be inserted as UCode is Primary key and 4 is already existing and so we
a) Name the attributes of EMPLOYEE, which can be used as candidate keys.b) The company wants to retrieve details of dependent of a particular employee. Name the tables and the key which are required to retrieve this detail.c) What is the degree of EMPLOYEE and DEPENDENT relation? Ans: (a) AadharNumber, EmployeeID (b) To retrieve the
a) To store each item name along with its price, what relation should be used?Decide appropriate attribute names along with their data type. Each item and its price should be stored only once. What restriction should be used while defining the relation?Ans: We will create new relation BILL to keep bill details as per the
a) Roll no 24 may not be interested in sports. Can a NULL value be assigned to that student’s preferences field? Ans: Yes, a NULL value can be assigned. b) Roll no 17 has given two preferences sports. Which property of relational DBMS is violated here? Can we use any constraint or key in the
The limitation if file systems that can be overcome by a relational DBMS are: Data Redundancy: redundancy means repetition of same data in different tables. Redundancy leads to excess data storage and may cause data inconsistency. Data Inconsistency: When same data is managed differently in different places leads to data inconsistency. Data inconsistency creates unreliable
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By storing data in different tables which are logically related, a database management system avoids redundancy in data through a database.
Degree Cardinality Total no of columns(attribute) in table Total no of rows (tuple) in a table Degree of multiple tables are always added Cardinality of multiple tables are always multiplied.
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Primary Key Foreign Key It identifies the each record in a table uniquely. It maintains the relation between two tables. A foreign key is primary key in another related table. A table can have only one Primary key. A table can have more than one Foreign key. Primary key cannot have NULL values. Foreign key
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Database Schema Database State Database Schema represent overall design of the database. Database state represent current state of data in database. Database schema is changed ocassionally Database state is changed frequently Initially when defining a database, only Database schema is specified Initially when defining a database, database state is empty state.
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