LEARNING PHP AND MYSQL (2015)

Data controls

The Data Control Language (DCL) allows users to access and manipulated data. Its main statements are as follow.

· GRANT allows one or more than one user to perform an operation on an object.

· REVOKE to eliminate a default grant.

Example

GRANT SELECT, UPDATE

ON example

TO some_user, another_user;

REVOKE SELECT, UPDATE

ON example

FROM some_user, another_user;

It carries out functions such as connect insert, select, update, execute and delete.

Procedural extensions

The designing of SQL is done in a form of query contained relation database. The procedural extension diagram of SQL is shown below. This allows programming contained in form of routines which. Some elements known in procedural extension of SQL are as follows.

· Polymorphism with the parameters in SQL of IN, OUT and INOUT modes.

· Various procedures calling statement.

· Atomic BEGIN and END call.

· Locally declared SQL statement.

· Error signaling and cursor processing.

· Declared data types.

· Various conditional control and looping statement.

Procedural extension

Drawbacks

· Portability do lack between database systems.

· Implementation is not supported with entire freedom because of the size and complexity of the SQL.

· The behavior of the implementation at several regions of database is confusing some times.

· There is little commercial incentive to vendors to enforce it as an easier task for the user to bring any changes in database suppliers.

· User’s evaluation of database software avoids factors such as higher performances for the standard priority.

Performance issue

· SQL has also been found to have a conflict in compatibility with the consumer’s prior database.