SQL Server documentation uses this notation, which is very easy to understand and consume. Is this a BNF Syntax Diagram? Or is this a different type of notation?


Source: SQL server documentation page with the original diagram

  • 7
    Railroad diagram. This looks like fun, I'll have to play with it now I found it ....
    – davidbak
    Apr 21, 2021 at 2:10
  • It's also a stylized version of finite state machine diagraming
    – Telastyn
    Apr 21, 2021 at 2:47
  • Is anyone aware of diagramming tools or stencils that allow these to be drawn easily by hand? The curved divergences and convergences are both aesthetically pleasing, and very useful for conveying the intended direction of flow.
    – Steve
    Apr 21, 2021 at 14:19
  • @Steve - if you're willing to write your diagram in the form of a grammar, the tool I linked above will do a nice job for you ...
    – davidbak
    Apr 22, 2021 at 4:02
  • @davidbak, indeed special tools that will generate diagrams from a grammar abound, I'm just surprised that the stylistic features of these diagrams (including the small repeater arrows which are ofren shown, though not in the example in the question) have not been incorporated into mainstream diagramming tools.
    – Steve
    Apr 22, 2021 at 8:51

1 Answer 1


It is a type of syntax diagram called a railroad diagram. See also here, here, and here.

Thanks to @davidbak who found the answer.

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