Hi Andy,
I believe that you see this behavior because the unique constraint does
not give rise to a unique index. The index forbids duplicates if all of
the key values are non-null. However, if any of the key values are null,
then duplicates are allowed. If you need an index which forbids
duplicate nulls, then you can use the CREATE INDEX statement.
Hope this helps,
-Rick
On 6/28/11 7:56 AM, Andy Jefferson wrote:
On Tuesday 28 Jun 2011 15:27:18 Andy
DataNucleus (http://www.datanucleus.org) Jefferson wrote:
If I create a unique index like this
ALTER TABLE {tblName} ADD CONSTRAINT {constrName} UNIQUE (col1, col2, col3)
and then call DatabaseMetaData.getIndexInfo()
it returns
tableCat =
tableSchem = null
tableName = tblName
columnName = col1
nonUnique = true
ordinalPosition = 1
indexName = SQL110628145704820
tableCat =
tableSchem = null
tableName = tblName
columnName = col2
nonUnique = true
ordinalPosition = 2
indexName = SQL110628145704820
tableCat =
tableSchem = null
tableName = tblName
columnName = col3
nonUnique = true
ordinalPosition = 3
indexName = SQL110628145704820
I ought to mention that on the same case MySQL returns the correct index name,
and returns false on the "nonUnique", hence I have all information necessary
