Structured Query language(SQL)

Structured Query language(SQL) originally developed by IBM at Alamden Research Center for its system - R project. It has become a de facto standard for most commercial DBMS. Majority of commercially available database management system has adopted SQL as relational database query language. The SQL language used for data definition, data manipulation, view maintenance, writing triggers, providing integrity control, security and remote database access. Now, the basis for formation of an SQL query.

    Consider the following schema.

    Student-scheme = (Roll_No, Student_Name, Marks)

    Hostel-scheme = (Hostel_Code, hostel_Name, Warden)

    Allot-scheme = (Roll_No, Hostel_Code)

We further denote that Student, Hostel and Allot are relation based on Student-scheme, Hostel-scheme and Allot-scheme respectively i.e.

    STUDENT(Student-Scheme)

    HOSTEL(Hostel-Scheme)

    ALLOT(Allot-scheme)

These relations are shown in the following tables. Note that STUDENT relation contain the data about Roll number, name and marks obtained by student. Hostel relation contain the data about Hostel name and warden name. The relation ALLOT contains the information about student and hostel allotted.

Student Table:

Roll_No	Student_Name	Marks
1	Ajay	78
2	Rajiv	56
3	Raghu	97
4	Rohil	86
5	Pankaj	55
6	Alok	60
7	Sanjeev	81
8	Arun	74
9	Sudhir	66
10	Sanjay	58

Hostel Table:

Hostel_Code	Hostel_Name	Warden
VA	Vivekanand	B N Mishra
RA	Raman	A. Mittal
KA	Krishna	G. Chandra

Allot Table:

Roll_No	Hostel_Code
1	VA
2	KA
3	RA
4	VA
5	RA
6	VA
7	RA
8	KA
9	KA
10	VA