Slide 9.1: Relational databases and database tables

Slide 8.22: Division
Slide 9.2: SQL (Structured Query Language)
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Relational Databases and SQL

Relational Databases
The relational model has a structural part (schemata with dependencies) and an operational part (relational algebra). The logical and physical levels are independent of each other. The only basic construct on the logical level is the relation; relations can be illustrated for the users in the form of tables.

student
student_id	last_name	first_name	class	phone
1	Jones	Allan	2	555-1234
2	Smith	John	3	555-4321
3	Brown	Harry	2	555-1122
5	White	Edward	3	555-3344

course
course_no	course_name	room	time
101	French I	2-104	MW2
102	French II	2-113	MW3
105	Algebra	3-105	MW2
108	Calculus	2-113	MW4

enrollment
student_id	course_no	major
1	101	No
1	108	Yes
2	105	No
3	101	Yes
3	108	No
5	102	No
5	105	No

What Can SQL (Structured Query Language) Do?

SQL can execute queries against a database.
SQL can retrieve data from a database.
SQL can insert records in a database.
SQL can update records in a database.
SQL can delete records from a database.
SQL can create new databases.
SQL can create new tables in a database.
SQL can create stored procedures in a database.
SQL can create views in a database.
SQL can set permissions on tables, procedures, and views.

Demonstration
Below is an SQL test area from W3Schools, which uses the well-known Northwind sample database. The tables here are for read only because of the problem of embedding the scripts. For a fully working example, check this by using Chrome.

Result:

The Database includes:

Tablename	Record
Customers	91
Categories	8
Employees	10
OrderDetails	518
Orders	196
Products	77
Shippers	3
Suppliers	29

W3C WebSQL

WebSQL Browser Support