In Oracle SQL, aliases and the DISTINCT clause are used to control and manipulate the presentation of data in query results. They help make query results more readable and allow you to eliminate duplicate rows from the result set. Here’s a brief description of aliases and the DISTINCT clause:

1. Aliases:

• Purpose: Aliases are used to assign temporary names or labels to columns or tables in the query. They make query results more readable and provide a way to rename columns or tables for presentation purposes.
• Syntax:
  • Column Alias (for renaming columns):SELECT column_name AS alias_name FROM table_name;
  • Table Alias (for renaming tables):SELECT t1.column1, t2.column2 FROM table1 t1 INNER JOIN table2 t2 ON t1.columnX = t2.columnY;
• Use Cases: Aliases are commonly used for renaming columns to provide more meaningful or concise names in the result set. They can also be used to alias table names when multiple tables are involved in a query.

2. DISTINCT Clause:

• Purpose: The DISTINCT clause is used to eliminate duplicate rows from the result set, ensuring that only unique rows are displayed.
• Syntax:SELECT DISTINCT column1, column2, ... FROM table_name;
• Use Cases: The DISTINCT clause is used when you want to retrieve only the unique values from one or more columns in the result set. It is particularly useful for finding unique values in a given dataset.

3. Examples:

• Column Alias Example:SELECT first_name AS "First Name", last_name AS "Last Name" FROM employees; In this example, the AS keyword is used to assign column aliases, making the result set more human-readable.
• Table Alias Example:SELECT o.order_id, c.customer_name FROM orders o INNER JOIN customers c ON o.customer_id = c.customer_id; Here, table aliases (o and c) are used to reference tables with shorter and more convenient names in the query.
• DISTINCT Clause Example:SELECT DISTINCT department FROM employees; This query retrieves only the distinct department names from the employees table, eliminating duplicate entries.

Aliases and the DISTINCT clause enhance the readability and precision of SQL queries. Aliases provide descriptive names for columns and tables, while the DISTINCT clause filters out duplicate rows, ensuring that the result set contains only unique values. These features are valuable tools for data presentation and analysis in Oracle SQL.