Скачать или смотреть How to Delete Books Published After 1985 Without Errors in PostgreSQL

Learn how to delete books published after 1985 from both book and author_book tables in PostgreSQL without encountering errors.
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When working with databases, there are often scenarios in which you need to remove data from multiple related tables. In this post, we'll explore how to delete books published after 1985 from both the book and author_book tables in PostgreSQL without running into errors.

Understanding the Schema

To effectively perform this deletion, let's first understand the structure of our tables:

book: This table contains information about books, including the publication year.

author_book: This table handles the relationship between authors and books, ensuring a many-to-many relationship.

Step-by-Step Guide to Deleting Records

We'll use SQL's DELETE statement, ensuring that we handle dependencies correctly and avoid referential integrity violations.

Involving a Transaction

We'll wrap our delete operations within a transaction to ensure data consistency. Here's how you can do it:

[[See Video to Reveal this Text or Code Snippet]]

Explanation

BEGIN; and COMMIT;: These statements start and commit the transaction respectively, ensuring that both deletes happen atomically. If an error occurs, you can rollback to maintain the integrity of your database.

DELETE FROM author_book:

We delete records in the author_book table first using a subquery to find all book_ids of books published after 1985.

Using IN ensures that we only target specific rows that meet the criteria.

DELETE FROM book:

After cleaning up the author_book table, we then proceed to delete the relevant rows from the book table containing books published after 1985.

Avoiding Errors

Order of Deletion: Ensuring that you delete from author_book first before book prevents foreign key constraint violations.

Transactional Integrity: Wrapping these statements in a transaction guarantees that either all changes occur, or none do, thus maintaining database consistency.

Conclusion

Carefully planning and executing delete operations ensures the integrity of your database. Follow the steps outlined to successfully delete books published after 1985 from both book and author_book tables without encountering errors in PostgreSQL.