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Thread: JDBC: what exactly does nullsAreSortedHigh() return?

JDBC: what exactly does nullsAreSortedHigh() return?

From
vikasrana@techie.com (Vikas Rana)
Date:
Hi all,

  I am a bit confused about the method
java.sql.DatabaseMetaData.nullsAreSortedHigh(). What exactly does this
return? If this returns true, are nulls considered as the highest
value? Or does this mean that nulls comes first when sorted in
ascending order (opposite in meaning to the first).

Consider this.

- Oracle returns false. Nulls are last when sorted in ascending order.

- MSSQL2K returns true. Nulls are first when sorted in ascending
order.

- Postgres returns true. Nulls are last when sorted in ascending
order.

Now, behavior of Oracle and Postgres is same in terms of sort order,
but they return different values.

Who is right?

Re: JDBC: what exactly does nullsAreSortedHigh() return?

From
Derek Chen-Becker
Date:
Vikas Rana wrote:
> Hi all,
>
>   I am a bit confused about the method
> java.sql.DatabaseMetaData.nullsAreSortedHigh(). What exactly does this
> return? If this returns true, are nulls considered as the highest
> value? Or does this mean that nulls comes first when sorted in
> ascending order (opposite in meaning to the first).
>
> Consider this.
>
> - Oracle returns false. Nulls are last when sorted in ascending order.
>
> - MSSQL2K returns true. Nulls are first when sorted in ascending
> order.
>
> - Postgres returns true. Nulls are last when sorted in ascending
> order.
>
> Now, behavior of Oracle and Postgres is same in terms of sort order,
> but they return different values.
>
> Who is right?

Here's the info from JDK1.4.2:

nullsAreSortedHigh

public boolean nullsAreSortedHigh()
                            throws SQLException

     Retrieves whether NULL values are sorted high. Sorted high means
that NULL values sort higher than any other value in a domain. In an
ascending order, if this method returns true, NULL values will appear at
the end. By contrast, the method nullsAreSortedAtEnd indicates whether
NULL values are sorted at the end regardless of sort order.

     Returns:
         true if so; false otherwise
     Throws:
         SQLException - if a database access error occurs


So it seems that both Oracle and MSSQL are wrong...

Derek

Re: JDBC: what exactly does nullsAreSortedHigh() return?

From
Lee Fesperman
Date:
Vikas Rana wrote:
>
> Hi all,
>
>   I am a bit confused about the method
> java.sql.DatabaseMetaData.nullsAreSortedHigh(). What exactly does this
> return? If this returns true, are nulls considered as the highest
> value? Or does this mean that nulls comes first when sorted in
> ascending order (opposite in meaning to the first).
>
> Consider this.
>
> - Oracle returns false. Nulls are last when sorted in ascending order.
>
> - MSSQL2K returns true. Nulls are first when sorted in ascending
> order.
>
> - Postgres returns true. Nulls are last when sorted in ascending
> order.
>
> Now, behavior of Oracle and Postgres is same in terms of sort order,
> but they return different values.
>
> Who is right?

It seems that the Oracle driver is wrong. I interpret nullsAreSortedHigh() the same as
Postgres.

That is, a true return from nullsAreSortedHigh() means Nulls are last when sorted in
ascending order.

This is the interpretation that FirstSQL/J uses.

--
Lee Fesperman, FirstSQL, Inc. (http://www.firstsql.com)
==============================================================
* The Ultimate DBMS is here!
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