Slide 7.4: SQL syntax (cont.)

SQL Syntax (Cont.)

SQL can be divided into two parts:

Data Manipulation Language (DML) and
Data Definition Language (DDL).

SQL Data Manipulation Language (DML)
The query and update commands form the DML part of SQL:

SELECT: Extract data from a database.
UPDATE: Update data in a database.
DELETE: Delete data from a database.
INSERT INTO: Insert new data into a database.

SQL Data Definition Language (DDL)
The DDL part of SQL permits database tables to be created or deleted. It also define indexes (keys), specify links between tables, and impose constraints between tables. The most important DDL statements in SQL are

CREATE DATABASE: Create a new database.
CREATE TABLE: Create a new table.
ALTER TABLE: Modify a table.
DROP TABLE: Delete a table.
CREATE INDEX: Create an index (search key).
DROP INDEX: Delete an index.

Using SQL in Your Web Site
To build a database-driven web site, the following is needed at least:

An RDBMS database (e.g., MS Access, SQL Server, MySQL),
A server-side scripting language, like PHP or ASP,
SQL, and
HTML and CSS.

Demonstration
The following is an SQL test area from W3Schools, which uses the well-known Northwind sample database and the tables are for read only.

For security reasons, the following demonstration may only work in Chrome.

Result:

Click “Run SQL” to execute the SQL statement above.

W3Schools has created an SQL database in your browser.

The menu to the right displays the database, and will reflect any changes.

Feel free to experiment with any SQL statement.

You can restore the database at any time.

The Database includes:

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

SQL Statement:

Result:

W3C WebSQL

WebSQL Browser Support