SQL can be divided into two parts:
- Data Manipulation Language (DML) and
- Data Definition Language (DDL).
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.
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
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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.
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
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.
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Result:
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The Database includes:
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The Database includes:
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