From 68212b93b0364cc71295bc9fe909b2d536a58326 Mon Sep 17 00:00:00 2001
From: ribardej <ribardej@student.cvut.cz>
Date: Thu, 18 Sep 2025 13:48:09 +0200
Subject: [PATCH] feat(design) created an ER diagram

---
 design.md | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/design.md b/design.md
index 38f20b1..0da1efd 100644
--- a/design.md
+++ b/design.md
@@ -63,6 +63,41 @@ flowchart LR
 - Example records or schemas (link to files or include concise snippets).
 - Users, Transactions, Transaction_Categories, User_settings
 
+```mermaid
+erDiagram
+    USERS {
+        int user_id PK
+        string name
+        string email
+    }
+
+    TRANSACTIONS {
+        int transaction_id PK
+        int user_id FK
+        int category_id FK
+        decimal amount
+        date transaction_date
+    }
+
+    TRANSACTION_CATEGORIES {
+        int category_id PK
+        string name
+        string type
+        string color
+    }
+
+    USER_SETTINGS {
+        int setting_id PK
+        int user_id FK
+        string setting_key
+        string setting_value
+    }
+
+    USERS ||--o{ TRANSACTIONS : "makes"
+    USERS ||--o{ USER_SETTINGS : "has"
+    TRANSACTION_CATEGORIES ||--o{ TRANSACTIONS : "categorizes"
+```
+
 ### 2.3 APIs (REST/gRPC/GraphQL)
 
 - Swagger