January 30, 2020
Amitraj
Reduction of ER diagram to Table -
-> ER diagram is converted into the tables in relational model.
-> This is because relational models can be easily implemented by RDBMS like MySQL , Oracle etc.
-> The database can be represented using the notations, and these notations can be reduced to a collection of tables.
-> In the database, every entity set or relationship set can be represented in tabular form.
ER Diagram:-
Following rules are used for converting an ER diagram into the tables -
1. Entity type becomes a table.
-> In the given ER diagram, LECTURE, STUDENT, SUBJECT and COURSE forms individual tables.
2. All single-valued attribute becomes a column for the table.
-> In the STUDENT entity, STUDENT_NAME and STUDENT_ID form the column of STUDENT table. Similarly, COURSE_NAME and COURSE_ID form the column of COURSE table and so on.
3. A key attribute of the entity type represented by the primary key.
-> In the given ER diagram, COURSE_ID, STUDENT_ID, SUBJECT_ID, and LECTURE_ID are the key attribute of the entity.
4. The multivalued attribute is represented by a separate table.
-> In the student table, a hobby is a multivalued attribute. So it is not possible to represent multiple values in a single column of STUDENT table. Hence we create a table STUD_HOBBY with column name STUDENT_ID and HOBBY. Using both the column, we create a composite key.
5. Composite attribute represented by components.
-> In the given ER diagram, student address is a composite attribute. It contains CITY, PIN, DOOR#, STREET, and STATE. In the STUDENT table, these attributes can merge as an individual column.
6. Derived attributes are not considered in the table.
-> In the STUDENT table, Age is the derived attribute. It can be calculated at any point of time by calculating the difference between current date and Date of Birth.
-> Using these rules, you can convert the ER diagram to tables and columns and assign the mapping between the tables. Table structure for the given ER diagram is as below:
-> ER diagram is converted into the tables in relational model.
-> This is because relational models can be easily implemented by RDBMS like MySQL , Oracle etc.
-> The database can be represented using the notations, and these notations can be reduced to a collection of tables.
-> In the database, every entity set or relationship set can be represented in tabular form.
ER Diagram:-
Following rules are used for converting an ER diagram into the tables -
1. Entity type becomes a table.
-> In the given ER diagram, LECTURE, STUDENT, SUBJECT and COURSE forms individual tables.
2. All single-valued attribute becomes a column for the table.
-> In the STUDENT entity, STUDENT_NAME and STUDENT_ID form the column of STUDENT table. Similarly, COURSE_NAME and COURSE_ID form the column of COURSE table and so on.
3. A key attribute of the entity type represented by the primary key.
-> In the given ER diagram, COURSE_ID, STUDENT_ID, SUBJECT_ID, and LECTURE_ID are the key attribute of the entity.
4. The multivalued attribute is represented by a separate table.
-> In the student table, a hobby is a multivalued attribute. So it is not possible to represent multiple values in a single column of STUDENT table. Hence we create a table STUD_HOBBY with column name STUDENT_ID and HOBBY. Using both the column, we create a composite key.
5. Composite attribute represented by components.
-> In the given ER diagram, student address is a composite attribute. It contains CITY, PIN, DOOR#, STREET, and STATE. In the STUDENT table, these attributes can merge as an individual column.
6. Derived attributes are not considered in the table.
-> In the STUDENT table, Age is the derived attribute. It can be calculated at any point of time by calculating the difference between current date and Date of Birth.
-> Using these rules, you can convert the ER diagram to tables and columns and assign the mapping between the tables. Table structure for the given ER diagram is as below:
