claude@clouddev1
6e42a118a3
The C5a design: a stratified, recursive WHERE-expression grammar (AND/OR/NOT, comparisons, LIKE, IS NULL, IN, BETWEEN) for update / delete / show-data filters; show data gains optional `where` and `limit`. Adds the `Subgrammar` reference-following grammar node and a recursive `Expr` AST, built selectively for the expression fragment. - docs/adr/0026-complex-where-expressions.md — the ADR. - docs/adr/README.md — index entry. - docs/simple-mode-limitations.md — new running list of simple-mode query boundaries vs. advanced SQL, seeded from ADR-0026. - docs/requirements.md — C5a [~] -> [ ] (designed, not yet implemented); new Documentation section with DOC1.
41 lines
1.5 KiB
Markdown
41 lines
1.5 KiB
Markdown
# Simple-mode query limitations
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Simple mode's DSL query surface is deliberately a *subset*
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of SQL. The DSL is a teaching on-ramp; advanced mode (raw
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SQL) is the full surface. This document is the running
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list of what a simple-mode query cannot express that
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advanced-mode SQL can.
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It serves two audiences:
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- **Students** — each entry is the seed of a short
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explanation of why the boundary exists and what to use
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instead (often: switch to advanced mode).
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- **Designers** — the consolidated list feeds the future
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`Q4` SQL-subset specification: the inverse view of what
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the supported subset deliberately leaves out.
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The list grows as new simple-mode surface lands; each
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entry names the ADR that drew the boundary.
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## WHERE expressions (ADR-0026)
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- **Comparison operands are a column or a literal**, not a
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nested expression. `(a > b) = (c > d)` — comparing two
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boolean sub-expressions — cannot be written. Parentheses
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group boolean sub-expressions, not comparison operands.
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- **A bare column is not a boolean.** A predicate always
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has an operator: write `Active = true`, not `Active`.
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- **No arithmetic** in expressions (`Price * 1.1`).
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- **No string concatenation.**
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- **No scalar functions** (`upper(Name)`, `length(x)`, …).
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- **No subqueries**, and no `EXISTS`.
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## Query shape (ADR-0026)
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- **No `ORDER BY`.** `show data … limit <n>` orders
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implicitly by the primary key; explicit ordering is not
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yet available.
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- **No `LIMIT … OFFSET`** — `limit` takes a row count
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only.
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