Unterschiede

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--- modul:m290:learningunits:lu05:theorie:01 [2024/09/25 10:40] – vdemir
+++ modul:m290:learningunits:lu05:theorie:01 [2024/10/24 12:50] (aktuell) – vdemir
@@ Zeile 1: / Zeile 1: @@
-====== LU06a - SQL-DDL: DB Management ======
+====== LU07a - SQL-DDL: DB Management ======
 ===== Learning Objectives =====
 In this session, we will learn some thrilling details about how to properly manage our databases. To achieve this, we need to know more about:
+  - What a db schema / db instance is.
   - How to create database instances.
   - How to display all currently available instances.
   - How to connect to one specific db-instance.
   - how you can delete obsolete or no longer required databases.
-  - How to import pre-pared databases that are ready for immediate use.
+=====  DB Schema vs. DB Instance =====
+A database schema and a database instance are related concepts in the context of a database system, but they refer to different aspects:
+{{:modul:m290:learningunits:lu05:theorie:1545889164421.jpg?400|}}
+==== 1. Database Schema ====
+The schema is the structure or blueprint that defines how data is organized within the database. It describes the database's logical design, including:
+  * **Tables**: The individual entities (e.g., Customers, Orders).
+  * **Columns**: The attributes of each entity (e.g., CustomerID, OrderDate).
+  * **Constraints**: Rules applied to the data (e.g., primary keys, foreign keys, unique constraints).
+  * **Relationships**: How tables relate to one another (e.g., one-to-many, many-to-many relationships).
+  * **Views, indexes, triggers, and stored procedures**: Other elements that define how the data is accessed or managed.
+Think of the schema as the blueprint or structure of the database that remains mostly static or changes rarely.
+==== 2. Database Instance: ====
+The instance refers to the actual data stored in the database at a particular point in time. It is the current state of the database, including all of the records or entries inside the tables defined by the schema.
+  * It includes actual rows of data in the tables.
+  * The instance can change frequently as data is inserted, updated, or deleted.
+  * You can think of the instance as the current snapshot of the database contents, while the schema defines the permanent framework.
+==== Analogy ====
+The schema is like the blueprint of a building (defining rooms, walls, and layout), while the instance is like the current state of the building (furniture, people inside, and their positions, which can change).
 ===== Access to the db with Webstorm code editor =====