Structured Query Language (SQL)

Structured Query Language (SQL) is the language used to manipulate relational databases. SQL is tied very closely with the relational model.

In the relational model, data is stored in structures called relations or tables.

SQL statements are issued for the purpose of:

Data definition: Defining tables and structures in the database (DDL used to create, alter and drop schema objects such as tables and indexes).

Data manipulation: Used to manipulate the data within those schema objects (DML Inserting, Updating, Deleting the data, and Querying the Database).

A schema is a collection of database objects that can include: tables, views, indexes and sequences

List of SQL statements that can be issued against an Oracle database schema are:

·         ALTER - Change an existing table, view or index definition (DDL)

·         AUDIT - Track the changes made to a table (DDL)

·         COMMENT - Add a comment to a table or column in a table (DDL)

·         COMMIT - Make all recent changes permanent (DML - transactional)

·         CREATE - Create new database objects such as tables or views (DDL)

·         DELETE - Delete rows from a database table (DML)

·         DROP - Drop a database object such as a table, view or index (DDL)

·         GRANT - Allow another user to access database objects such as tables or views (DDL)

·         INSERT - Insert new data into a database table (DML)

·         No AUDIT - Turn off the auditing function (DDL)

·         REVOKE - Disallow a user access to database objects such as tables and views (DDL)

·         ROLLBACK - Undo any recent changes to the database (DML - Transactional)

·         SELECT - Retrieve data from a database table (DML)

·         TRUNCATE - Delete all rows from a database table (can not be rolled back) (DML)

·         UPDATE - Change the values of some data items in a database table (DML)