Data retrieving using the SQL SELECT command.

Basic SELECT Statement

SELECT *|{[DISTINCT] column|expression [alias],...} FROM table;

SELECT identifies the columns to be displayed.
FROM identifies the table containing those columns.

Selecting All Columns 

SELECT * FROM departments;

Selecting Specific Columns 

SELECT department_id, location_id FROM departments;

Writing SQL Statements(Conventions)

• SQL statements are not case-sensitive.
• SQL statements can be entered on one or more lines.
• Keywords cannot be abbreviated or split across lines.
• Clauses are usually placed on separate lines.
• Indents are used to enhance readability.
• In SQL Developer, SQL statements can optionally be terminated by a semicolon (;).
• Semicolons are required when you execute multiple SQL statements.
• In SQL*Plus, you are required to end each SQL statement
  with a semicolon (;).