Скачать или смотреть DB 2026 02 14

The video provided is a lecture titled "DB 2026 02 14" from the Advanced Database Systems (Haladó Adatbáziskezelő Rendszerek) course, taught by István Ványi. The lecture covers administrative course information, system integration strategies, and database replication.

1. Course Administration and Overview
Requirements: Grading is based on five short tests (50%) and a final project (50%) [10:07].

Schedule: The semester includes several "marathon" sessions and both personal and online consultations [06:07].

Infrastructure: Students use a pre-configured virtual machine containing Microsoft SQL Server, PostgreSQL, and Neo4j for hands-on exercises [23:45].

2. System Integration: Tight vs. Loose Coupling
The lecturer presents a real-world industrial case study involving the integration of an ERP system with a separate Quality Assurance system [30:19].

Tight Coupling (Risk): Using a trigger to immediately update another system is risky. If the secondary system fails or the trigger has an error (e.g., division by zero), it can crash the primary ERP system and prevent any orders from being saved [40:21].

Loose Coupling (Solution): Instead of direct updates, a trigger is used to save the event into a "log table." A scheduled Job then processes these logs asynchronously. This ensures that a failure in the processing step does not affect the operation of the primary system [43:19].

Technical Implementation: The demo shows how to create log tables, write robust triggers, use cursors for processing events one by one, and configure the SQL Server Agent to run these tasks [46:03].

3. Database Replication Concepts
The latter half of the lecture focuses on replication, which is the automated copying of data between servers [02:04:39].

Roles: Replication involves three main roles: the Publisher (source), the Distributor (manages the flow), and the Subscriber (destination) [02:06:51].

Snapshot Replication: This method takes a "picture" of the data and overwrites the subscriber's table entirely at set intervals. It is simple but can cause high network traffic and temporary table unavailability [02:13:22].

Transactional Replication: This is the most common professional method. It monitors the Transaction Log for changes and propagates only the specific updates, inserts, or deletes to the subscriber, ensuring low latency and high consistency [02:40:48].

4. Practical Demonstrations
The instructor performs live configurations on SQL Server, showing:

Setting up a Distributor and Publisher [02:21:56].

Creating a Snapshot publication for specific filtered data (e.g., US orders only) [02:26:54].

Setting up Transactional replication across three different server instances (Primary, Second, Third) to demonstrate real-time data flow [02:46:11].