RE: Order in left join

Lukasz Misztal wrote:

> Hello everyone,
>
> i have a simple question:
> is order of fields in (left) join in MAXDB significant?
>
> For example:
>
> select * from "Table1"
> left join "Table2" on "Table1_ID"="Table2_IDTable1"
>
> Returns:
> 10 21 10
> 11 ? ?
>
> but
>
> select * from "Table1"
> left join "Table2" on "Table2_IDTable1"="Table1_ID"
>
> Returns:
> ? 20 ?
> 10 21 10
>
> I get confused.
> Two diffrent strategies (JOIN VIA KEY RANGE/JOIN VIA KEY COLUMN).
>
> I have searched bugs.mysql.com but it gets nothing.
> Is it bug whether my basic mistake?
>
> Lukasz
>
> ---------------------
> MAXDB 7.6.00.37 WinXp prof., test data:
>
> CREATE TABLE "Table1"
> (
> "Table1_ID" Fixed (12,0),
> PRIMARY KEY ("Table1_ID")
> )
> //
> CREATE TABLE "Table2"
> (
> "Table2_ID" Fixed (12,0),
> "Table2_IDTable1" Fixed (12,0),
> PRIMARY KEY ("Table2_ID")
> )
> //
> insert into "Table1" values (10)
> //
> insert into "Table1" values (11)
> //
> insert into "Table2" values (20,null)
> //
> insert into "Table2" values (21,10)
> //
> select * from "Table1"
> left join "Table2" on "Table2_IDTable1"="Table1_ID"
> //
> select * from "Table1"
> left join "Table2" on "Table1_ID"="Table2_IDTable1"

Hi,

Lars explanation is not correct the order of the predicate in the on clause of an outer join should have no influence on the result. The LEFT and RIGHT refers to the table from which you want to see every row regardless if the on clause is qualified or not. If you have TAB_A LEFT JOIN TAB_B ON TAB_A.X = TAB_B.Y you will see every row from TAB_A regardless if there is a corresponding row in TAB_B. And if you have TAB_B LEFT JOIN TAB_A ON TAB_A.X = TAB_B.Y you want to see all rows from TAB_B regardless if there is a corresponding row in TAB_A.

So this is definitely a bug within MaxDB and we will fix it with the next version. For detailed information about error processing see http://www.sapdb.org/webpts?wptsdetail=yes&ErrorType=0&ErrorID=1149721

As a workaround you could use explicit tablename specification.

In my test this example works:

select * from "Table1" left join "Table2" on "Table2"."Table2_IDTable1"="Table1"."Table1_ID" select * from "Table1" left join "Table2" on "Table1"."Table1_ID"="Table2"."Table2_IDTable1"

Do you need help?

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Sorry for any inconvenience and thank you for reporting this bug.

Best regards
Holger

Holger Becker
MaxDB&liveCache
SAP AG
www.sap.com
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