[rjb32]

Follow-up to #20. Its second commit was pushed a moment after #20 was merged, so it never reached main. This PR is that commit, cherry-picked onto main unchanged.

What

New page, NEXT and WHEN (query/composition, in the nav after Results and aggregation). The NEXT and WHEN sections move there from Results and aggregation.

• NEXT: passing nodes to the next step, longer chains, after a UNION, braced chains as UNION sides, inside CALL / EXISTS / COUNT, writes, and the scoping and alias rules.
• WHEN ... THEN ... ELSE: several branches, subquery conditions (WHEN EXISTS {...}, WHEN COUNT {...} > 3), per row after NEXT and in CALL, behaviour without ELSE, NEXT chains in a branch, UNION, writes, and rules.

More examples on existing pages

• COLLECT { }:
  • WHERE, DISTINCT, top-k with ORDER BY / LIMIT, UNION, collected nodes
  • use in WHERE / UNWIND / SET
  • its limits: one column, a full query, no maps, NEXT or WHEN inside
• Other subqueries: UNION bodies for EXISTS and COUNT, and CALL bodies that write and return what they wrote.
• FOREACH: edges off a matched node, several clauses per element, list properties (converted with toString), conditional writes with the CASE trick, RETURN after it.
• Parameters: inside label expressions, in WHERE n:$label, numbered $0, MERGE labels and edge types, and both error messages.
• Functions and other syntax:
  • examples for the string, normalize, conversion and statistical functions
  • keywords as map keys
  • label expressions in OPTIONAL MATCH and WHERE NOT
  • quantified-path group variables in UNWIND / ORDER BY
  • ASCENDING / DESCENDING

How it was checked

• Every cypher example in query/ (332 statements) was run against a 3.0.2 server, on the sample graph from the matching page.
  • Every new or changed example passes with the expected rows.
  • The 6 remaining failures need fixtures the test setup lacks (Stations graph, my_index, knows.csv, the greeter extension, two multi-command blocks).
• The edge cases behind each rule were probed on the same server: what NEXT, WHEN and COLLECT accept and reject, and the exact error messages.
• npm run build passes (43 pages), and every new internal link resolves.