A better way to code ?

Question

There was this select statement and will return lines along with its flag (status). Though I don't like the query itself, it uses MIN on a CHAR field. But it works. the open_flag value on both table will only be 'Y', 'N' or NULL. It's a CHAR(1).
SELECT (SELECT DECODE(l.open_flag, 'N', 'N', NVL(MIN(s.open_flag), 'Y'))
FROM my_shipping_v s
WHERE s.order_line_id = l.line_id) update_flag, l.LINE_NUMBER
FROM my_order_line_v l
WHERE order_id = variable_order_id
AND link_to_line_id IS NULL;
ORDER BY line_number;
Is there a simple modification to the query to find out if any update_flag = 'N' ? (from both table).
Will exists works? I tried couple of ways, no luck yet.

Answer 1

This?
SELECT update_flag, line_number
FROM   (SELECT DECODE(l.open_flag, 'N', 'N', NVL(MIN(s.open_flag), 'Y')) update_flag,
               l.line_number
        FROM   my_order_line_v l, my_shipping_v s
        WHERE  s.order_line_id = l.line_id
        AND    order_id = variable_order_id
        AND    link_to_line_id IS NULL)
WHERE  update_flag = 'N'
ORDER BY line_number;NB. I took the correlated subquery out of the select clause and incorporated it as a join in the main query - looks neater that way. I think the performance will be the same, but you'd need to check. My gut feel is that Oracle would rewrite your query into a join.
Message was edited by:
Boneist
Or by the same token, if you'd prefer not to have the query wrapped in an outer select, you could do:
SELECT DECODE(l.open_flag, 'N', 'N', NVL(MIN(s.open_flag), 'Y')) update_flag,
       l.line_number
FROM   my_order_line_v l, my_shipping_v s
WHERE  s.order_line_id = l.line_id
AND    order_id = variable_order_id
AND    link_to_line_id IS NULL
AND    DECODE(l.open_flag, 'N', 'N', NVL(MIN(s.open_flag), 'Y')) = 'N'
ORDER BY l.line_number;