Working with Multiple Tables Notes

Editing and Deleting Tables

  • Editing Tables: To change the structure of a table, such as adding, deleting, or modifying fields:
    • Open the table in Design View.
    • Modify field names, data types, or add new fields as needed.
  • Deleting Tables: If a table is no longer needed, you can delete it:
    • Right-click on the table name and choose “Delete” from the menu.
    • Be cautious, as deleting a table permanently removes all the data within it.

Relationships Between Tables

  • Relationship: A relationship is a link between two tables based on a common field. Relationships help connect related data across multiple tables, making it easy to organize and retrieve information.

Types of Relationships

  • One-to-One Relationship: Each record in Table A has only one matching record in Table B, and vice versa. Example: A student table and a library card table where each student has only one library card.
  • One-to-Many Relationship: A record in Table A can have multiple matching records in Table B, but each record in Table B has only one match in Table A. Example: A customer table and an orders table where each customer can place many orders, but each order is linked to only one customer.
  • Many-to-Many Relationship: Records in Table A can have multiple matching records in Table B, and records in Table B can have multiple matches in Table A. Example: A students table and a courses table, where each student can enroll in multiple courses, and each course can have many students.

Advantages of Relating Tables in a Database

  • Data Organization: Relating tables reduces data duplication and helps keep the database organized.
  • Easy Data Retrieval: Related tables make it simpler to gather related data through queries.
  • Improved Data Accuracy: By connecting tables, databases can prevent redundant or conflicting information.
  • Efficient Data Management: Managing related tables improves performance and helps save storage space.

Creating Relationships Between Tables

  • To create a relationship:
    • Open the Relationships window in LibreOffice Base.
    • Drag a field (usually the primary key) from one table to the matching field in another table.
    • Set the relationship type (One-to-One, One-to-Many, etc.) and confirm.

Referential Integrity

  • Referential Integrity: This rule ensures that relationships between tables remain consistent. If a record in one table is related to records in another table, referential integrity makes sure that changes in one table don’t break the link in another.
  • Purpose:
    • Prevents accidental deletion of records that are related to others.
    • Keeps data accurate and reliable across related tables.

These concepts form the foundation of working with multiple tables in a database, helping students understand how data can be efficiently managed and interconnected for better organization and retrieval.

 

By Jitendra Singh

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