IBM DB2 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 IBM DB2 parser includes a lexer lookahead mechanism that allows 23 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 between FROM t;

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

-- Original keyword syntax also still works

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Full Classification Overview

Out of 573 keywords recognized by the GSP IBM DB2 parser:

Classification	Count	Description
Allowed	547	Can be used as an unquoted column name in both canonical contexts
Context-specific	25	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 (25)

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
BETWEEN	Operator keyword
BLOB	Type keyword
CASE	Expression keyword
CAST	Expression keyword
CURRENT	Grammar keyword
CURSOR	Grammar keyword
DISTINCT	SELECT qualifier
IN	Operator keyword
JOIN	JOIN keyword
LIKE	Operator keyword
LISTAGG	Grammar keyword
MICROSECOND	Grammar keyword
MINUTE	Grammar keyword
PRIOR	Grammar keyword
RIGHT	JOIN keyword
SECOND	Grammar keyword
SUBSTRING	Expression keyword
UNION	Clause keyword
UNIQUE	Grammar keyword
XMLCAST	Grammar keyword
XMLELEMENT	Grammar keyword
XMLQUERY	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 IBM DB2

Methodology

1. Static extraction: A Python script parses the lexer (.cod) and grammar (.y) source files to identify all 573 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/db2_keyword_compatibility.json.