Data independence described as the property of database management system that helps the user in changing the schema of database at one level of the database system without need to change the schema at next and higher level. Data independence help in keeping the data separated from all different programs that make use out of it. In Database management system, there are two types of data independence. First is logical data independence and second is physical data independence.
Physical data independence helps the user in separating the internal or physical level from the conceptual level. It permits the user to offer a logical description of the database and there is no need to specify the physical structure if the data base. If compare both the logical dependence then it easy to accomplish physical data independence.
With the help of physical data independence, user can transform the physical structure of storage easily and also change the physical device easily with an impact on the conceptual schema. Any change can execute with the help of mapping among internal and conceptual levels. IT can be accomplished with the help of internal level of database and then change from the conceptual to the internal level of database.
Physical data independence is achieved by the presence of the internal level of the database and then the transformation from the conceptual level of the database to the internal level.
A primary key is used to access the record of the customers from the table. If there is no primary key in the table then the table leads to computation artifacts.
Primary key is the basic aspect to create a table.
File processing system
Database Management System
The problem of redundancy cannot be controlled in the file system
The issue of redundancy can be controlled in Database management system.
A file system offers loose guarantee of various problems like consistency, durability and isolation.
Database is very much consistent all the time, it provides durable writes and
The file processing system can only coordinate with the physical access of the database.
A database system provides coordination with both to access the data, the physical and logical access.
There is no restriction on the unauthorized access in DBMS
There is restriction on the unauthorized in DBMS
Relation is called table sometimes in the relational database but generally it is used to describe the relationship among tables used in the relational database. Every component in the relation is known as attribute value. It is the name of the value A relation is a table in the relational database because it used to store the relation among data in its row-column format.
The columns are the relation’s attribute while data records are represented with the rows.
Tuple is the single row to the database designers.
A relation schema is a set of attributes. It is also known as table schema. A relation schema is also used to represent the basic structure of the table and it also give the information about the table or relation.
Relation schema is the definition but a logical one of the tables. It is also used to describe the name of the table. It also includes the number of column of tables, and the data type associated with each each attribute.
Relational schema is also known as database schema. It is used to describe the prototype of database that used in a manner data is structured in the database.
Null is the special name used in SQL that is structured query language. It is used to indicate that the value of data does not exist in the database. The concept of Null value is introduced by the creator of relational database which is E.F.Codd.
Null is used to meet all the requirements of the RDBMS that is Relational database management system. It supports, “inapplicable information” and “missing information” to represent in database.
A null value shows the lack of value, it does not mean 0. Likewise, the lack of answer that does not mean the user don’t know the answer.
SELECT titles of course
FROM Comp. Sci department
WHERE credits =4.
SELECT instructor name
FROM Physics department
Where Salary > Lowest
SELECT enrollment number
FROM student Table
WHERE enrollment number =Fall 2009
From Section Table
SELECT course ID and Section ID
FROM section table
HAVING count (enrollment number) = minimum;
SELECT DISTINCT Student names,
FROM Computer sci department
WHERE Courses >= 2;
b. Find the IDs and names of all students who have not taken any course offering in 2009.
SELECT IDs and student name
From Student table
GROUP BY IDs
HAVING =offering in 2009;
c. For each department, find the name and salary of the instructor who earns the minimum salary in that department. You may assume that every department has at least one instructor.
SELECT instructor salary
FROM Department Table
Where Salary =Minimum
ORDER BY SALARY DESC;
d. Find the highest, across all departments, of the per-department minimum salary computed by the preceding query.
SELECT instructor salary
FROM Department Table
Where Salary =Maximum
ORDER BY Salary;
e. Find the course titles of all prerequisite courses of “CS-319”.
SELECT course Title
FROM course table
HAVING prerequisite courses = “CS-319”;
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