[DERBY-5893] Add support for the SQL:2008 standard IS [ NOT ] DISTINCT FROM predicate

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 10.9.1.0
• Component/s: SQL
• Labels: derby_triage10_10 features
• Urgency: Normal
• Assignee: Unassigned
• Reporter: Lukas Eder
• Created: 04/Aug/12 15:09
• Updated: 28/Sep/12 02:15

Description

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.