23.03.11 12:19, Adarsh Sharma написав(ла):
Vitalii Tymchyshyn wrote: 23.03.11 12:10, Adarsh Sharma написав(ла): I just want to retrieve that id 's from page_content which do not have any entry in clause2 table.
Then
select distinct(p.crawled_page_id) from page_content p
where NOT EXISTS (select 1 from clause2 c where c.source_id = p.crawled_page_id);
is correct query.
I can't understand how select 1 from clause2 c where c.source_id = p.crawled_page_id works too, i get my output .
What is the significance of 1 here.
No significance. You can put anything there. E.g. "*". Simply arbitrary constant. Exists checks if there were any rows, it does not matter which columns are there or what is in this columns.
Best regards, Vitalii Tymchyshyn