Planning a Database: An Example: -

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In Relational Database Management Systems (RDBMS) data are represented using tables (relations). A query issued against the RDBMS also results in a table. A table has the following structure:





























Column 1 Column 2 --------- Column n
--- ---- ---- ----
       
       

A table is uniquely identified by its name and consists of rows that contain the stored information, each row containing exactly one tuple (or record). A table can have one or more columns. A column is made up of a column name and a data type, and it describes an attribute of the tuples. The structure of a table, also called relation schema, thus is defined by its attributes. The type of information to be stored in a table is defined by the data types of the attributes at table creation time.


SQL uses the terms table, row, and column for relation, tuple, and attribute, respectively. A table can have up to 254 columns which may have different or same data types and sets of values (domains), respectively.


Before creation of the database we will find out the Tables, Table attributes and data types of the attributes. We will take the example of School Management System Database. This includes the details about the teachers, courses, students and marks. The following are structures of the tables in the system: -


Tables Used in the Database: - Teacher, Course, Student, Marks
Structure of the tables: -

Teacher



























Attribute Name Data Type
TeacherID Number(10)
TeacherName Varchar2(30)
Qualification Varchar2(30)
Subject Varchar2(30)
ContactNumber Number(10)



Course



























Attribute Name Data Type
CourseID Number(5)
CourseName Varchar2(30)
TotalCredits Number(3)
No_ofSubjects Number(2)
TeacherID Number(10)

Student























Attribute Name Data Type
StudentID Number(10)
StudentName Varchar2(30)
Address Varchar2(30)
CourseID Number(5)

Marks







































Attribute Name Data Type
StudentID Number(5)
MarksObtained Number(4)
MarksPercentage Number(4,2)
Marks_Sub1 Number(2)
Marks_Sub2 Number(2)
Marks_Sub3 Number(2)
Marks_Sub4 Number(2)
Marks_Sub5 Number(2)

 
                    

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