Creating Subgraphs With Rank

Ranking is useful whenever you want certain nodes to align visually in a consistent row or column. By placing nodes into a shared subgraph with a defined rank, you can control the layout and make structural relationships easier to understand. Common scenarios include:

• Grouping Peers: Aligning team members, departments, or sibling categories on the same horizontal level to emphasize equal standing.
• Highlighting Stages: Showing phases of a project or lifecycle (e.g., Planning, Execution, Review) on a single rank for clarity.
• Organizing Layers: Keeping all “input” nodes at the top, “processing” nodes in the middle, and “output” nodes at the bottom.
• Comparing Alternatives: Placing multiple options or branches side‑by‑side so users can visually compare them.
• Clarifying Hierarchies: Ensuring that children of the same parent appear on the same rank, preventing uneven or zig‑zag layouts.
• Creating Swimlanes: Using ranks to form horizontal lanes that separate categories, roles, or functional areas.
• Stabilizing Layouts: When Graphviz’s automatic layout shifts nodes unpredictably, explicit ranks help lock the structure into a predictable shape.

These scenarios benefit from the CREATE RANK extension because it gives you precise control over how nodes align, making your graphs cleaner, more readable, and more intentional.

Assume you have an Excel workbook containing a worksheet named Alphabet with a column heading letter and four rows of data: A, B, C, and D. You want all of these nodes to appear on the same rank.

The CREATE RANK SQL extension produces subgraphs whose nodes share the same rank.

The SQL is specifed as follows:

SELECT [letter] AS [Item], 
      TRUE      AS [CREATE RANK], 
      'same'    AS [RANK] 
FROM [Alphabet$]

The SQL above results in one row added to the data worksheet with:

• Item = >
• Label = {rank="same"; "A"; "B"; "C"; "D";}

The values you can pair with RANK are same, min, source, max, and sink. The Graphviz rankdir attribute appears to treat these values as case‑sensitive, so be sure to specify them in lowercase.