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7-CIE 9618
The normalisation process
发布于: 2024-11-9
最后更新: 2026-3-18
次查看
concepts
目录
0%
Context of the Statement
The SQL Statement
Breaking Down the Statement
1. ALTER TABLE Orders
2. ADD FOREIGN KEY (CustomerAddress)
3. REFERENCES Addresses(CustomerAddress)
Why Add a Foreign Key Constraint?
1. Enforce Referential Integrity
2. Data Consistency and Accuracy
3. Simplify Database Maintenance
Detailed Example
Before Adding the Foreign Key Constraint
After Adding the Foreign Key Constraint
Understanding Each Component Further
ALTER TABLE
ADD FOREIGN KEY
REFERENCES
What Happens Internally When You Add a Foreign Key Constraint
1. Validation of Existing Data
2. Enforcing the Constraint for Future Operations
Handling Deletions and Updates
Specifying Actions on DELETE and UPDATE
Syntax with ON DELETE and ON UPDATE
Options:
Example:
Why Use CustomerAddress Instead of an ID?
Alternate Approach: Using AddressID
Advantages of Using AddressID:
Why Use CustomerAddress Here?
Ensuring Data Types Match
Possible Errors and How to Fix Them
Error When Adding Constraint
Error When Deleting Referenced Data
Checking the Constraint
Verify Constraint Exists
Summary of Key Points
Final Thoughts
Additional Resources
How to use the database created above:
1. Understanding the Tables
2. How to Use the Tables
3. Understanding Normalization Steps
4. Best Practices
5. Sample Queries for Practice
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目录
0%
Context of the Statement
The SQL Statement
Breaking Down the Statement
1. ALTER TABLE Orders
2. ADD FOREIGN KEY (CustomerAddress)
3. REFERENCES Addresses(CustomerAddress)
Why Add a Foreign Key Constraint?
1. Enforce Referential Integrity
2. Data Consistency and Accuracy
3. Simplify Database Maintenance
Detailed Example
Before Adding the Foreign Key Constraint
After Adding the Foreign Key Constraint
Understanding Each Component Further
ALTER TABLE
ADD FOREIGN KEY
REFERENCES
What Happens Internally When You Add a Foreign Key Constraint
1. Validation of Existing Data
2. Enforcing the Constraint for Future Operations
Handling Deletions and Updates
Specifying Actions on DELETE and UPDATE
Syntax with ON DELETE and ON UPDATE
Options:
Example:
Why Use CustomerAddress Instead of an ID?
Alternate Approach: Using AddressID
Advantages of Using AddressID:
Why Use CustomerAddress Here?
Ensuring Data Types Match
Possible Errors and How to Fix Them
Error When Adding Constraint
Error When Deleting Referenced Data
Checking the Constraint
Verify Constraint Exists
Summary of Key Points
Final Thoughts
Additional Resources
How to use the database created above:
1. Understanding the Tables
2. How to Use the Tables
3. Understanding Normalization Steps
4. Best Practices
5. Sample Queries for Practice
