| Introduction to Web Development |
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| Basic PHP Syntax |
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| PHP Basics |
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| Variables and Data Types |
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| Functions in PHP |
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| User-defined Functions |
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| Built-in Functions |
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| Variable Scope |
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| Include and Require |
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| Working with Forms |
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| Forms in HTML |
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| Form Handling in PHP |
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| Working with Files |
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| File Handling |
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| File System Functions |
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| Working with Databases |
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| Introduction to Databases |
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| Advanced PHP Techniques |
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| Object-Oriented Programming (OOP) |
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| Error and Exception Handling |
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Database design and normalization are critical aspects of creating an efficient and effective database system. Let’s delve into each of these topics in detail.
Database Design
1. Requirements Analysis
- Gathering Requirements: The first step involves understanding the needs of the business or application. This includes identifying what data needs to be stored, the relationships between different data items, and the operations that will be performed on the data.
- Defining Scope: Clearly outline the boundaries of the database project to ensure it meets the necessary requirements without unnecessary complexity.
2. Conceptual Design
- Entity-Relationship Diagram (ERD): This diagram visually represents the entities (objects or things of interest), attributes (properties of the entities), and relationships (associations between the entities) in the database.
- Entities: These are the objects or things in the system, e.g., Customer, Order, Product.
- Attributes: These are the details we want to store about each entity, e.g., Customer Name, Order Date, Product Price.
- Relationships: These define how entities are related to each other, e.g., a Customer places an Order.
3. Logical Design
- Schema Definition: Converting the ERD into a relational schema. This involves defining tables, columns, primary keys, and foreign keys.
- Normalization: Ensuring the schema is free from redundancy and anomalies by organizing the data into multiple related tables.
4. Physical Design
- Storage Considerations: Deciding how the data will be stored, indexed, and accessed on the physical storage media.
- Performance Optimization: Designing the database for efficient querying, which may include denormalization for read-heavy applications or using indexing strategies.
5. Implementation
- SQL Scripts: Writing SQL scripts to create tables, define relationships, and set up constraints.
- Data Migration: Moving existing data into the new database structure, if applicable.
6. Testing and Refinement
- Testing: Ensuring the database meets all requirements and performs well under load.
- Refinement: Making necessary adjustments based on feedback and testing results.
Normalization
Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. It involves decomposing tables into smaller, more manageable pieces without losing information. There are several normal forms (NF), each addressing specific types of redundancy.
1. First Normal Form (1NF)
- Atomicity: Ensure each column contains only atomic (indivisible) values. Each value in a column should be of the same type.
- Unique Rows: Ensure each row is unique.
2. Second Normal Form (2NF)
- 1NF Compliance: The table must be in 1NF.
- Full Functional Dependency: Ensure that all non-key attributes are fully functionally dependent on the primary key. This means no partial dependency on any subset of the primary key.
3. Third Normal Form (3NF)
- 2NF Compliance: The table must be in 2NF.
- No Transitive Dependency: Ensure that no non-key attribute is transitively dependent on the primary key. This means non-key attributes should not depend on other non-key attributes.
4. Boyce-Codd Normal Form (BCNF)
- 3NF Compliance: The table must be in 3NF.
- Stricter Conditions: Ensure that every determinant is a candidate key. This addresses certain anomalies not covered by 3NF.
5. Fourth Normal Form (4NF)
- BCNF Compliance: The table must be in BCNF.
- Multi-valued Dependency: Ensure no table contains two or more independent multi-valued facts about an entity.
6. Fifth Normal Form (5NF)
- 4NF Compliance: The table must be in 4NF.
- Join Dependency: Ensure that every join dependency in the table is a consequence of the candidate keys.
Example of Normalization
Suppose we have the following table that stores information about orders, customers, and products:
| OrderID | CustomerName | CustomerAddress | ProductID | ProductName | Quantity |
|---|---|---|---|---|---|
| 1 | Alice | 123 Maple St | 101 | Widget | 10 |
| 2 | Bob | 456 Oak St | 102 | Gadget | 5 |
| 1 | Alice | 123 Maple St | 103 | Doodad | 7 |
Unnormalized Table: The table above has redundancy, as Alice’s information is repeated.
1NF: Ensure atomicity by splitting multi-valued attributes.
- The table is already in 1NF as each column contains atomic values.
2NF: Remove partial dependencies.
- Split the table into two tables to separate orders and products:
Orders Table:
| OrderID | CustomerName | CustomerAddress |
|---|---|---|
| 1 | Alice | 123 Maple St |
| 2 | Bob | 456 Oak St |
OrderDetails Table:
| OrderID | ProductID | ProductName | Quantity |
|---|---|---|---|
| 1 | 101 | Widget | 10 |
| 1 | 103 | Doodad | 7 |
| 2 | 102 | Gadget | 5 |
3NF: Remove transitive dependencies.
- Separate the customer information from the orders:
Customers Table:
| CustomerName | CustomerAddress |
|---|---|
| Alice | 123 Maple St |
| Bob | 456 Oak St |
Orders Table:
| OrderID | CustomerName |
|---|---|
| 1 | Alice |
| 2 | Bob |
OrderDetails Table remains the same.
BCNF: Ensure that every determinant is a candidate key.
- The tables above already satisfy BCNF as all determinants are candidate keys.
4NF and 5NF: Check for multi-valued and join dependencies.
- The current design is free from such dependencies.
This example demonstrates the process of normalization, resulting in a database design that minimizes redundancy and ensures data integrity.
