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GeezerVison is showing github.com — DuckDB: accept FROM-first queries and TABLE t as subqueries and set operands by guizmaii · Pull Request #2799 · JSQLParser/JSqlParser

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@guizmaii

@guizmaii guizmaii commented Oct 13, 2026 •
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For DuckDB, where FROM-first queries (docs) and TABLE t are queries like any other:

Input Before After
SELECT * FROM (FROM t), a IN (FROM u), (FROM u SELECT max(a)) error sub-select
FROM a UNION ALL FROM b, SELECT 1 EXCEPT FROM b WHERE x error SetOperationList of FROM-first PlainSelects
TABLE a UNION TABLE b ORDER BY 1, (TABLE a EXCEPT ALL TABLE b) error SetOperationList of TableStatements, ORDER BY on the list
WITH t AS (SELECT 1) TABLE t error TableStatement with its WITH items, deparsed
  • isParenthesedSelectAhead() / isParenthesedFromItemAhead() accept (FROM, and (TABLE when a table name follows and then ), a set operator, ORDER, LIMIT, OFFSET or FETCH. So (table = 'hits'), (table) and (table.a) stay expressions on a column named table (ClickHouse's system.parts), and Oracle's TABLE(...) is untouched.
  • In Select(), FROM-first selects and TableStatement join the alternatives that can be followed by a set operation; SetOperationList accepts them as operands and hoists a trailing ORDER BY/LIMIT/OFFSET from a last TableStatement as it does for a PlainSelect. The separate TableStatement() statement alternative is now covered by Select().
  • isFromFirstSelectAhead() also recognises a following set operator, stops at the end of the enclosing parentheses, and follows the token chain instead of calling getToken(i) per token. A bare FROM t, also parenthesized, and pipe queries are still FromQuery.
  • TableStatement uses Select.appendTo, and TableStatementDeParser prints the WITH clause, OPTION, FETCH and the isolation level. CREATE TABLE ... AS takes any query, e.g. TABLE a UNION TABLE b; FROM (TABLE s.t) x now parses.
  • All these inputs were errors in every dialect. On ~9,760 statements extracted from this repository's tests, parse results, statement types and output are identical to master for everything that parsed there.
  • checkGrammarAmbiguity: no conflicts. ./gradlew check: 10,116 tests, 0 failures.
  • DuckDB's own test suite (test/sql, 70,729 statements): 155 more parse, none less.

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guizmaii added 2 commits October 13, 2026 19:51
@guizmaii
DuckDB: accept FROM-first queries and TABLE t as subqueries and set o…
c62e4ee
…perands

- `(FROM t ...)` is a sub-select wherever `(SELECT ...)` is, and a
  parenthesized `FROM t` without pipe operators is a FROM-first select.
- FROM-first queries and `TABLE t` are set operation operands, e.g.
  `FROM a UNION ALL FROM b` or `TABLE a EXCEPT TABLE b`, with a trailing
  ORDER BY/LIMIT applying to the whole operation.
- `WITH ... TABLE t` keeps and prints its WITH clause.
- The FROM-first scan follows the token chain and stops at the end of
  the enclosing parentheses.
@guizmaii
Keep columns named table and print every clause of TABLE t
0cf6f83
- `(TABLE` starts a sub-select only when a table name follows and then
  the end of the query, so `(table = 'hits')` and `(table)` stay
  expressions on a column named table. `FROM (TABLE s.t) x` now parses.
- A parenthesized `FROM t` without clauses stays a `FromQuery`.
- `TableStatement` uses `Select.appendTo`, and its deparser prints
  OPTION, FETCH and the isolation level, so `TABLE t FETCH FIRST 1 ROWS
  ONLY` keeps its FETCH.
- `CREATE TABLE ... AS` takes any query, including `TABLE a UNION TABLE b`.
@guizmaii
guizmaii marked this pull request as ready for review October 13, 2026 09:12
Copilot AI balanced review requested due to automatic review settings October 13, 2026 09:12
Copilot AI reviewed Oct 13, 2026

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@guizmaii guizmaii mentioned this pull request Oct 13, 2026
DuckDB: remaining syntax to support #2804
Open
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@manticore-projects
manticore-projects merged commit 0deeafa into JSQLParser:master Oct 13, 2026
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@manticore-projects

manticore-projects commented Oct 13, 2026

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@guizmaii
guizmaii deleted the duckdb-from-first-operands branch October 22, 2026 23:12
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@guizmaii @manticore-projects
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