Here's the problem

IDX_COL1  IDX_COL_2
null      value1
null      value1

This does not violate a uniqueness constraint in H2.  NULL is considered a 
unique value.  Does this match the semantics of any other DBMS?

On Tuesday, March 27, 2018 at 10:21:23 PM UTC-7, Evgenij Ryazanov wrote:
>
> On Wednesday, 28 March 2018 00:11:29 UTC+8, Wes Clark wrote:
>>
>> We switched to Oracle mode so that unique indexes could allow multiple 
>> null values.  Is there a way to preserve that and still use the H2 date 
>> datatype?
>>
>
> In regular mode unique indexes allow multiple rows with NULL values too. 
> They are forbidden only in HSQLDB, Derby, and MSSQLServer modes.
>
> But if you use multi-column indexes there is a difference between regular 
> and Oracle mode.
>
> In Oracle mode only rows with NULL values in all indexed columns may be 
> duplicated.
> IDX_COL1  IDX_COL2
> null      null
> null      null
>
> In regular mode rows with NULL value in any indexed column may be 
> duplicated.
> IDX_COL1  IDX_COL_2
> null      null
> null      null
> null      value1
> null      value2
> value3    null
> value4    null
>
>

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