# KDB+ q SQL Vector Expression Parse Tree Explainer Parse q expressions and q-sql queries into an annotated tree showing right-to-left evaluation order, token classes, the functional select form and splayed-column attributes. > Canonical page: https://elysiatools.com/en/tools/kdb-plus-q-sql-vector-expression-parse-tree-explainer - **Category:** Data Visualization - **Keywords:** q parse tree, q right to left, kdb expression evaluator, functional select generator, q adverbs explained, splayed attribute reference ## Overview Implements q’s single evaluation rule (no operator precedence, left-of-right), adverb/iterator parsing, template query phrase splitting with the comma gotcha, functional-form generation, temporal casting (dates are day counts since 2000.01.01) and the four splayed attributes. ## Inputs - **q expression or select query** (textarea): select max price by sym from trade where date=2026.09.07, price>10 also try: 2*3+4 · +/ 1 2 3 · x:1 2 3; sum each x - **Show evaluation-order badges** (checkbox) - **Show functional form ?\[t;c;b;a\]** (checkbox) ## When to use - Debugging unexpected evaluation outcomes in nested vector arithmetic caused by q's lack of operator precedence. - Converting declarative q-sql select queries into equivalent functional select forms (?\[t;c;b;a\]) for dynamic execution. - Understanding the execution sequence of complex where clauses, temporal casts, and iterator or adverb modifications. ## How it works - Enter a raw q expression, vector operation, or q-sql query into the input area. - Toggle evaluation-order badges and the functional select form generator as needed. - The tool parses tokens, evaluates right-to-left reduction hierarchies, splits query phases, and outputs an annotated visual HTML tree. ## Use cases - Refactoring static q-sql analytical queries into dynamic functional select dictionaries for production APIs. - Training new kdb+/q developers on vector execution flow, temporal offsets, and right-to-left syntax mechanics. - Validating column filtering order and splayed table attribute applicability during query optimization. ## Frequently asked questions ### How does q evaluate arithmetic without operator precedence? q evaluates expressions strictly right-to-left (left-of-right), meaning operations on the right execute before operations on the left unless grouped by parentheses. ### What is the functional form generated by this tool? It generates the functional query structure ?[table; whereClause; byClause; selectClause] used for programmatic and dynamic q-sql queries. ### How does the tool handle temporal date values? Dates such as 2026.09.07 are parsed and displayed alongside their internal q representation as days elapsed since the epoch 2000.01.01. ### Does this tool identify iterator and adverb tokens? Yes, it parses adverbs and iterators like each, over (/), and scan (\) into token classes within the expression parse tree. ### What is the 'comma gotcha' in q-sql where clauses? 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