Kirill Tkalenko created IGNITE-29016:
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Summary: SQL Calcite: Support treating empty strings as NULL
Key: IGNITE-29016
URL: https://issues.apache.org/jira/browse/IGNITE-29016
Project: Ignite
Issue Type: Improvement
Reporter: Kirill Tkalenko
Assignee: Kirill Tkalenko
Some databases support treating zero-length character strings as {{{}NULL{}}}:
Oracle does this by default, while Db2 and H2 provide it through Oracle
compatibility modes.
[Oracle|https://docs.oracle.com/en/database/oracle/oracle-database/18/sqlrf/Nulls.html],
[Db2|https://www.ibm.com/docs/en/db2/12.1.x?topic=compatability-varchar2-nvarchar2],
[H2|https://h2database.github.io/html/features.html#compatibility_modes].
When enabled:
* String literals, parameters and stored values {{''}} are treated as
{{{}NULL{}}}.
* Empty strings returned by expressions, built-in functions, UDFs and UDTFs
become {{{}NULL{}}}.
* Comparisons follow regular SQL {{NULL}} semantics.
* A whitespace-only string such as {{' '}} remains unchanged.
* Binary values and LOBs are not affected.
The existing behavior should remain when the option is disabled.
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