GaussDB Keyword Compatibility Reference

Generated for GSP Java version 4.1.0.8 on 2026-03-15

This page was generated using hybrid static extraction from parser source files combined with runtime validation against the actual GSP parser. Re-run the extraction script after parser updates to keep this page current.

Keyword-as-Column-Name Support

As of version 4.1.0.8, the GSP GaussDB parser includes a lexer lookahead mechanism that allows 63 vendor-unreserved keywords to be used as unquoted column names in SELECT statements.

The lookahead pre-scans the token list before parsing and converts context-specific keywords to identifiers when they appear in column-name position:

• After: SELECT, ,, DISTINCT, or ALL
• Before: FROM, AS, WHERE, GROUP, ORDER, HAVING, LIMIT, UNION, INTERSECT, EXCEPT, INTO, ,, ), or ;

-- Works: keyword as column name
SELECT array FROM t;

-- Works: keyword as column name
SELECT authorization FROM t;

-- Works: keyword as column name
SELECT bigint FROM t;

-- Original keyword syntax also still works

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Full Classification Overview

Out of 584 keywords recognized by the GSP GaussDB parser:

Classification	Count	Description
Allowed	518	Can be used as an unquoted column name in both canonical contexts
Context-specific	65	Fails as SELECT keyword FROM t but works as SELECT t.keyword FROM t
Blocked	1	Cannot be used as an unquoted column name in either context

Context-Specific Keywords (65)

These keywords fail when used as bare column names (SELECT keyword FROM t) but succeed when table-qualified (SELECT t.keyword FROM t).

Keyword	Reason
ALL	SELECT qualifier
ARRAY	Type keyword
AUTHORIZATION	Grammar keyword
BIGINT	Type keyword
BOOLEAN	Type keyword
CASE	Expression keyword
CAST	Expression keyword
CHAR	Type keyword
CHARACTER	Type keyword
COALESCE	Expression keyword
COLLATION	Grammar keyword
CONCURRENTLY	Grammar keyword
CROSS	JOIN keyword
DECIMAL	Type keyword
DISTINCT	SELECT qualifier
DOUBLE	Type keyword
EXISTS	Operator keyword
FLOAT	Type keyword
FLOAT4	Type keyword
FLOAT8	Type keyword
FREEZE	Grammar keyword
FULL	JOIN keyword
GREATEST	Expression keyword
GROUP_CONCAT	Grammar keyword
ILIKE	Operator keyword
INT2	Type keyword
INT4	Type keyword
INT8	Type keyword
INTEGER	Type keyword
INTERVAL	Type keyword
INTO	Clause keyword
IS	Operator keyword
JOIN	JOIN keyword
LEAST	Expression keyword
LEFT	JOIN keyword
LIKE	Operator keyword
NATIONAL	Type keyword
NATURAL	JOIN keyword
NCHAR	Type keyword
NOT	Operator keyword
NULLIF	Expression keyword
NUMERIC	Type keyword
OUTER	JOIN keyword
OVERLAPS	Operator keyword
OVERLAY	Expression keyword
PERCENTILE_CONT	Grammar keyword
PERCENTILE_DISC	Grammar keyword
REAL	Type keyword
RIGHT	JOIN keyword
SIMILAR	Operator keyword
SMALLINT	Type keyword
SUBSTRING	Expression keyword
TREAT	Expression keyword
TRY_CAST	Grammar keyword
UNIQUE	Grammar keyword
VARCHAR	Type keyword
VERBOSE	Grammar keyword
XMLCONCAT	Grammar keyword
XMLELEMENT	Grammar keyword
XMLEXISTS	Grammar keyword
XMLFOREST	Grammar keyword
XMLPARSE	Grammar keyword
XMLPI	Grammar keyword
XMLROOT	Grammar keyword
XMLSERIALIZE	Grammar keyword

Blocked Keywords (1)

These keywords cannot be used as unquoted column names in either context.

Keyword	Workaround
FROM	SELECT "from" FROM t

Workaround: Double-Quoted Identifiers

For any keyword that fails as an unquoted column name, you can use double-quoted identifiers:

-- Blocked or context-specific keyword as column name
SELECT "from" FROM t;

-- Or use table qualification for context-specific keywords
SELECT t.all FROM t;

Scope and Limitations

• Tested contexts: SELECT keyword FROM t and SELECT t.keyword FROM t. Other contexts (DDL column definitions, INSERT column lists, aliases) may behave differently.
• Version-specific: This report reflects GSP Java version 4.1.0.8.
• Case sensitivity: Keywords are case-insensitive. select, SELECT, and Select are all treated the same.

How to Report Discrepancies

If you encounter a keyword that behaves differently from what this page describes, please report it through your support channel. Include:

1. The exact SQL statement
2. The GSP parser version
3. Whether the same SQL works in GaussDB

Methodology

1. Static extraction: A Python script parses the lexer (.cod) and grammar (.y) source files to identify all 584 keywords and their grammar classifications.
2. Runtime validation: A Java test harness validates every classification against actual TGSqlParser runtime behavior.
3. JSON dataset: The authoritative data is stored in docs/generated/gaussdb_keyword_compatibility.json.