Great question! Let me break this down for you—Draw.io (now rebranded as Diagrams.net) does support visualizing foreign key relationships for SQL databases, but getting it to work might require adjusting your approach instead of relying solely on pasting raw SQL snippets. Here's how to make it work reliably:

Step 1: Start with the Right Template #

First, don't start with a blank canvas. Open a new diagram and navigate to the Database category, then pick a template like Entity Relationship or your preferred SQL flavor (e.g., MySQL, PostgreSQL). This gives you pre-built table shapes, column fields, and dedicated relationship connectors that are designed for this exact use case.

Step 2: Define Relationships Manually (Most Reliable Method) #

If pasting SQL didn't generate the foreign key links you expected, this hands-on approach never fails:

• Add your table shapes to the canvas, fill in all primary key and foreign key columns.
• Grab the Relationship connector from the Database shape library (it looks like a line with optional cardinality markers).
• Drag it from the parent table's primary key column to the child table's corresponding foreign key column.
• Double-click the connector to tweak its properties: label it with the constraint name, set cardinality (1-to-many, etc.), or add notes about ON DELETE/ON UPDATE rules.

Why Your SQL Pasting Might Have Failed #

Draw.io's SQL import tool can be finicky with syntax, even for valid examples like the W3Schools ones. Common pitfalls include:

• Foreign key constraints defined as separate ALTER TABLE commands (the import tool often misses these—stick to defining them directly in the CREATE TABLE statement).
• Vendor-specific syntax (like MySQL's ENGINE=InnoDB flags or PostgreSQL's SERIAL types) that the parser doesn't recognize.
• Missing explicit PRIMARY KEY definitions (the tool needs clear primary key markers to map relationships).

For reference, here's a SQL snippet that should import correctly with foreign keys intact:

CREATE TABLE Customers (
    CustomerID int NOT NULL PRIMARY KEY,
    CustomerName varchar(255) NOT NULL
);

CREATE TABLE Orders (
    OrderID int NOT NULL PRIMARY KEY,
    CustomerID int,
    OrderDate date,
    FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID)
);

Pro Tip: Import Directly from a Live Database #

If you have access to a live database instance, this is the easiest way to get a fully connected ER diagram. Go to File > Import > Database, follow the prompts to connect via JDBC/ODBC, and Draw.io will auto-pull all tables, columns, and foreign key relationships for you—no manual work needed.

内容的提问来源于stack exchange，提问作者BrunoMartinsPro