Lukas Eder created DERBY-5893:
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Summary: Add support for the SQL:2008 standard IS [ NOT ] DISTINCT
FROM predicate
Key: DERBY-5893
URL: https://issues.apache.org/jira/browse/DERBY-5893
Project: Derby
Issue Type: Improvement
Components: SQL
Affects Versions: 10.9.1.0
Reporter: Lukas Eder
Priority: Minor
The SQL:1999 standard specifies the IS [ NOT ] DISTINCT FROM predicate in
chapter 8.15 <distinct predicate>:
<distinct predicate> ::=
<row value predicand 3> <distinct predicate part 2>
<distinct predicate part 2> ::=
IS [ NOT ] DISTINCT FROM <row value predicand 4>
<row value predicand 3> ::=
<row value predicand>
<row value predicand 4> ::=
<row value predicand>
This predicate is supported by at least these databases:
- http://www.postgresql.org/docs/9.1/static/functions-comparison.html
- http://www.h2database.com/html/grammar.html#condition_right_hand_side
- http://hsqldb.org/doc/guide/ch05.html#N11BB0
-
http://dev.mysql.com/doc/refman/5.6/en/comparison-operators.html#operator_equal-to
(with a different syntax)
-
http://dcx.sybase.com/1200/en/dbreference/is-distinct-from-search-condition.html
It would probably make sense for the Derby database to implement it as well.
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