Building SQA-style ER and entity-occurrence diagrams in draw.io

1. 1

   Go to app.diagrams.net. When asked where to save, choose Device.

2. 2

   Choose Create New Diagram, then Blank Diagram.

3. 3

   At the bottom of the left-hand shape panel, click More Shapes. Under the Software category, tick Entity Relation, then click Apply. This adds a set of ready-made connector ends for cardinality — you'll use these instead of drawing crow's feet by hand.

4. 4

   You should now see an extra shape section in the left panel with pre-styled ER connectors. Leave this open — you'll come back to it in the connectors section below.

draw.io's Entity Relation library also includes ready-made "database table" shapes with their own built-in primary/foreign key icons. Don't use those for Higher DDD — they don't look like SQA's expected notation. Use a plain rectangle with manually formatted text instead, so your diagram matches what an SQA answer is expected to look like.

1. 1

   From the General section of the left panel, drag a plain Rectangle onto the canvas.

2. 2

   Double-click the rectangle and type the entity name on the first line, then press Shift+Enter to add each attribute on its own line below it.

3. 3

   Highlight the primary key's text, then use the Format panel on the right (or the floating text toolbar) to apply underline.

4. 4

   For each foreign key, type an asterisk * directly after the attribute name — SQA's own convention, not a draw.io feature, so it's just typed text.

5. 5

   Resize the box using the blue handles if the text doesn't fit neatly.

Hover over an entity box until blue arrows appear, then drag from a blue arrow to another entity box to draw a connector. Double-click the connector to add its relationship name (a verb phrase, e.g. "generates").

1. 1

   Click the connector to select it, then open the Format panel on the right (or the Arrange tab → line-end options).

2. 2

   Use the dropdown arrows at each end of the line to pick a crow's-foot style. Hover over each option before choosing — the list includes several styles, not just the two you need.

3. 3

   Put a plain single-line end ("one") on the entity that is the "one" side of the relationship, and the crow's-foot ("many") end on the entity that is the "many" side.

An entity-occurrence diagram is simpler to build than an ER diagram — it just needs two tall ovals and a dot for each individual record, joined by plain connector lines. You don't need the Entity Relation library or any crow's-foot connector ends for this one.

1. 1

   From the General section of the left panel, drag two Ellipse shapes onto the canvas, tall and narrow, one for each entity. Label each one above the oval.

2. 2

   Add a small circle (or use the Ellipse shape resized very small) inside each oval for every individual record in your sample data. Label each dot with its record's ID.

3. 3

   Draw a plain connector line between two dots whenever those two specific records are linked — hover over a dot until the blue arrows appear, then drag to the other dot. Don't use any crow's-foot connector ends here; a plain line is all an EO diagram needs.

4. 4

   Once every line from your sample data is drawn, count the lines leaving each dot on both sides to work out the cardinality, then state it in words next to the diagram — a diagram without a stated cardinality doesn't get full marks.

1. 1

   Save your working file regularly with Ctrl+S (draw.io saves as a .drawio XML file) to your H drive.

2. 2

   When your diagram is finished, use File → Export As → PNG. Keep the default settings and click Export.

3. 3

   Save the PNG somewhere you can find it again, then use it to compare against the model answer in your lesson task.