ER diagrams

An ER diagram in Lume shows a part of your database: the tables you are working with and the foreign keys between them. It is built for large databases: the whole catalog stays searchable, but only what you choose is drawn.

Open a diagram

From	What opens
Right-click a table > Show ER Diagram	that table and the tables linked to it by one foreign key
Select several tables (Cmd+click each, or Shift+click a range), right-click > Show ER Diagram (N tables)	those tables, laid out together
Right-click a connection, its Tables group or a schema > New ER Diagram...	a picker: the most connected tables, the ones you pick, an empty diagram, or the whole schema when it is small
Tools > New ER Diagram... / Open ER Diagram...	the same, for the active connection / a saved diagram

Every diagram action is also in the command palette under "Diagram:".

Lume reads the structure in a few bulk queries (names, types, keys, comments: never rows), caches it, and never runs anything else on the connection. Diagrams are read-only: changing a table goes through the Table Designer, which shows the SQL before it runs.

What you see

• Cards: a key icon marks the primary key, FK a foreign key column; nullable columns are dimmer. Keys / Name / All on the toolbar chooses how much each card shows (per card too: right-click > Card).
• Lines: a solid line is a foreign key in the database. Crow's foot = many, bar = one, circle = optional (the column accepts NULL). Cardinality comes only from the database's keys; when it cannot be known, the end is neutral.
• +N on a card: N related tables are not on the diagram yet. Click it to add them.
• A dashed card is a table outside the diagram's scope (another schema, or one your login cannot read): a reference, not a missing relation.

Find

Cmd+F searches the whole scope, not only the cards drawn: tables, columns, constraints (foreign key names) and notes, with Contains / Prefix / Exact / Glob and Match case.

• Enter / Shift+Enter (or F3 / Shift+F3) go to the next / previous match and centre it.
• Going to a table that is not on the diagram yet adds exactly that table.
• from:orders to:customers finds the relations between two tables.

Move around

• Pan: drag the background, or scroll with two fingers.
• Zoom: pinch on the trackpad, Cmd+scroll, double-click the background (Shift+double-click zooms out), or – / 100% / + on the toolbar.
• Fit (Cmd+1) frames everything; Fit Selection (Cmd+2) the selection.
• Arrow keys move between cards; Cmd+[ / Cmd+] go back / forward through the places you visited.
• Far away, cards become boxes with their names; hover one to read it. More > View > Minimap shows where you are.

Organise

• Layout (Shift+Cmd+L) arranges the cards around the table you started from (deterministic: the same diagram always lays out the same way). Drag cards to place them; Pin keeps one in place. Cmd+Z undoes a move.
• Notes and group areas (More > Add Note / Add Group Area) document the diagram.
• Virtual relations: right-click a card > Draw Virtual Relation..., then click the other card. They are dashed, labelled "virtual", stored only in the diagram, and can be marked as verified with their evidence. They never create a foreign key.
• Business names: right-click > Business Name... and the Business names toggle show the names your business uses, with the table name beside them.
• Logical entities (More > Add Logical Entity) sketch a concept that is not a table yet.

The diagram is saved automatically in your workspace's diagrams folder (a readable .lume-erd file you can keep in Git). When a table changed since the diagram was saved, its card says changed.

Export

Export... on the toolbar: PNG, SVG, PDF, Mermaid, GraphML, draw.io or a self-contained HTML page (search, pan and zoom, no external requests), for the selection, the visible part or the whole diagram. The PDF holds an image of the diagram (one page); for sharp vector output use SVG or HTML. Copy as Image (Shift+Cmd+C) puts the selection on the clipboard.

Lume Intelligence

More > Lume Intelligence can explain the selected tables, suggest domain groups or suggest a conceptual map. Nothing is sent before a dialog shows exactly what would go (structure only: names, types, keys, comments; never rows). Suggestions are proposals you accept or reject one by one; a suggested relation is drawn dotted and never becomes a foreign key.