Question

I am not good in sql so please don’t scold me for such basic question. Currently I am doing a lot of homework on other technologies so I will improve sql as and when I get time to study it. Anyway let come to the point.

My question is for below query. I am trying to fetch data from three tables and it works fine as long as all conditions are satisfied but the problem is that for a posting it may happen that images are not present i.e not record for a posting in image table then post.post_id = img.post_id and img.sequence='1' condition fails and no row is returned but I want row to be returned even if no record present in images for the posting. In such case return null for image path column.

SELECT 
    img.path as path, pav.value_text as beds, post.post_id as postID 
FROM 
    postings post, post_attributes_values pav, images img 
where 
    post.post_id = pav.post_id and post.status !='expired' and pav.attr_id='33' and post.post_id = img.post_id and img.sequence='1' and post.post_id=49

If all condition satisfies then O/P comes like

    path                beds          postId
-----------------------------------------------
    saome path value     2             49

but if post.post_id = img.post_id and img.sequence='1' condition not satisfied then O/P should be like:

    path        beds          postId
----------------------------------------
    null         2              49

Answer 1

Use left outer join

SELECT 
    img.path as path, pav.value_text as beds, post.post_id as postID 
FROM 
    postings post 
    inner join post_attributes_values pav on post.post_id = pav.post_id and pav.attr_id='33' 
    left outer join images img on post.post_id = img.post_id and  img.sequence='1' 
where  post.status !='expired' and post.post_id=49