استرجاع البيانات باستخدام SQL - المعلوماتية

Database 2 - Lecture Notes

• Course: Business Information Systems
• Year: 2024-2025
• Class: Third Year
• Lecturer: Dr. Mohammed Elmetwaly
• Software: Oracle Database
• Topic: Retrieving Data Using SQL SELECT Statements

Objectives

• Writing SQL statements
• Running Oracle SQL
• Selecting all columns
• Selecting specific columns
• Clearing the screen
• Displaying the table structure
• Exiting SQL

Key SQL Concepts

• SQL statements are not case-sensitive.
• SQL statements can be entered on one or more lines.
• Do not use reserved words when creating objects.
• In SQL Plus, statements end with a semicolon (;).
• Running Oracle SQL: Steps outlined to start Oracle environment. (e.g., Start > Programs > Oracle > OraDB21-Home1 > SQL Plus)
• Selecting all columns: Use SELECT * FROM table_name;
• Selecting specific columns: SELECT column1, column2, … FROM table_name;
• Clearing the screen: Use CL SCR;
• Displaying table structure: Use DESCRIBE table_name; or DESC table_name;
• Exiting SQL: EXIT;
• SQL SELECT Statements Capabilities: Projection (selecting specific columns) and selection (retrieving rows meeting specific criteria).
• Valid SQL user: User account and password required (e.g., User: SCOTT, Password: TIGER, Database: ORCL).

SQL Tables and Data

• Retrieving all tables: SELECT * FROM tab; (Displays all tables for current user SCOTT)
• Example Data Retrieval: Illustrating how to retrieve data from tables (e.g., SELECT employee_id, last_name, job_id, department_id FROM employees; retrieves specific attributes from employee table)
• Specific Column Selection: Examples of selecting data from multiple columns (e.g., SELECT ename,job FROM emp;, SELECT empno,ename,sal FROM emp;, SELECT empno, ename, comm, hiredate FROM emp;)
• WHERE Clause: Using WHERE clause to fetch specific rows that match conditions. Illustrative example given.

Quiz Questions

• Criteria for writing a SQL statement
• Methods for displaying all columns in a table
• How to describe a table in the SQL environment
• SQL commands to clear the screen
• SQL commands to exit the environment