"WITH CREATEOBJECT('session')"
This is a kool construct. It would nver have crossed my mind. How did you end up doing it?

>If you declare a field not nullable, and index it ( like a id AUTOINC primary key ),
>and use it into a SELECT SQL,
>VFP can optimize it and use the index for search other SELECT fields with null values,
>BUT, if you search the same field value when it is outside of the query,
>VFP fire a index error.
>
>Repro:
>

>WITH CREATEOBJECT('session')
>	SET DATASESSION TO .DatasessionId
>	CLEAR
>	CREATE CURSOR myParent ( rId I UNIQUE)
>	FOR k=1 TO 10
>	  INSERT INTO myParent VALUES (M.K)
>	NEXT
>	ON ERROR ? 'ERROR >>>>>>>>>>   ',MESSAGE()
>
>	CREATE CURSOR myCursor( fkId i NULL)
>	INSERT INTO	myCursor VALUES (NULL)
>	SYS(3054,12)
>
>	SELECT myParent.* FROM myParent,myCursor WHERE myParent.rId=myCursor.fkId INTO ARRAY ZZ 	&& this not fire THE INDEX error
>	
>	SELECT myParent.* FROM myParent          WHERE myParent.rId=myCursor.fkId INTO ARRAY ZZ 	&& this     fire THE INDEX error
>		
>	
>*!*		SELECT myParent.* FROM myCursor X JOIN myParent ON myParent.rId=X.fkId AND myParent.rId=NULL	INTO ARRAY ZZ 	&& this     fire THE INDEX error
>*!*		SELECT myParent.* FROM myCursor X JOIN myParent ON myParent.rId=X.fkId AND myParent.rId IS NULL INTO ARRAY ZZ 	&& this not fire THE INDEX error
>*!*		SELECT myParent.* FROM myCursor X JOIN myParent ON myParent.rId=X.fkId OR  myParent.rId=NULL	INTO ARRAY ZZ	&& this not fire THE INDEX error
>
>	ON ERROR
>ENDWITH
>

>