Database Concepts

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What is an ER Diagram?

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A visual representation of how data in a database is organized and how different elements (entities) relate to each other.

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What are Implicit Cursors?

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A cursor that's automatically created and managed by the database system when certain SQL statements are executed, like SELECT INTO, INSERT, UPDATE, or DELETE.

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What are Explicit Cursors?

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A user-defined cursor that you declare, open, fetch from, and close manually in your PL/SQL code, allowing for complete control over the cursor's lifecycle, row-by-row processing, and custom logic.

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What does Atomicity ensure in a transaction?

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It ensures that either the entire transaction completes fully or doesn’t execute at all.

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What does Consistency ensure in a database?

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It ensures that a database remains in a valid state before and after a transaction.

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What does Isolation ensure in transactions?

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It ensures that multiple transactions can occur concurrently without leading to the inconsistency of the database state.

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What does Durability ensure in a transaction?

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It ensures that once the transaction has completed execution, the updates and modifications to the database are stored in and written to disk, persisting even if a system failure occurs.

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What is a Transaction in the context of databases?

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A transaction is a sequence of operations performed as a single logical unit of work, which must either be fully completed or fully failed to maintain data integrity.

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What is the purpose of a Database Management System (DBMS)?

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A DBMS is software that interacts with end users, applications, and the database itself to capture and analyze data, ensuring data integrity and security.

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What is a Primary Key in a database?

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A primary key is a unique identifier for a record in a database table, ensuring that no two records can have the same key value.