thanks for the reply, in my db the 2 columns Id are (NOT_NULL) PK, the nullable column is the FK Target, your query seems to get all the records where TARGET IS NOT NULL (b.Id is always not null).


anyhow at the moment i cannot test becouse i have another problem, in my final procedure i need to update same records based on that select.

this is my db
Table A
{
INTEGER ID; //PK (NOT-NULL)
INTEGER SOURCE: //NOT NULL FK TO ANOTHER TABLE
INTEGER TARGET; //NULLABLE FK TO TABLE B
}

Table B
{
INTEGER ID; //PK (NOT-NULL)
INTEGER VALUE; //NOT-NULL
}

i need to implement a procedure wich takes
integer NEW_TARGET_ID
integer SOURCE_ID
integer THRESHOLD

in this procedure i need to update the table A.
what i need is to update all the records where A.SOURCE = :Source_ID
and A.TARGET IS NULL or A.TARGET.VALUE < :threshold (pseudo code of the correct join).
for that records i need to update TARGET to :NEW_TARGET_ID

i'm tring to do samenthing as

update A
set A.TARGET = :NEW_TARGET_ID from A a left outer join B b....

but this doesn't compile. how i can update records matched with ths type of select?