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Data Visualization
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.
Details
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.
Execution
Fill in the form, run the tool, and review the result in one place.
Samples
Related
Tool usage guide
The KDB+ q SQL Vector Expression Parse Tree Explainer decomposes q expressions and q-sql queries into visual parse trees, highlighting right-to-left evaluation order, token classifications, and functional select forms.
Background
A developer needs to explain why standard arithmetic formulas yield unexpected values in q without parentheses.
Problem
Verify why the expression 2*3+4 evaluates to 14 instead of 10.
How to use
Input 2*3+4 and enable evaluation-order badges.
qCode: "2*3+4", showOrder: true, showFunctional: falseOutcome
A breakdown displaying the reduction step 3+4 -> 7 followed by 2*7 -> 14 with annotated evaluation order badges.
Background
A data engineer needs to construct parameterized queries against a partitioned historical database table.
Problem
Convert a declarative select query with multiple filter criteria and groupings into a dynamic ?[t;c;b;a] functional form.
How to use
Input the q-sql select statement and enable the functional form option.
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.
It generates the functional query structure ?[table; whereClause; byClause; selectClause] used for programmatic and dynamic q-sql queries.
Dates such as 2026.09.07 are parsed and displayed alongside their internal q representation as days elapsed since the epoch 2000.01.01.
Yes, it parses adverbs and iterators like each, over (/), and scan (\) into token classes within the expression parse tree.
In q-sql where phrases, commas act as sequential boolean filters evaluated left-to-right, short-circuiting downstream evaluations across columns.
Sample SQL scripts (DDL/DML, joins, CTEs) for the in-browser SQL Viewer
qCode: "select max price by sym from trade where date=2026.09.07, price>10", showOrder: true, showFunctional: trueOutcome
An annotated tree splitting Where/By/Select phrases alongside the equivalent ?[trade; ((=;`date;2026.09.07);(>;`price;10)); (enlist `sym)!enlist `sym; (max;`price)] syntax.