1

If you have, for example;

SELECT * FROM data 
WHERE line = min( (SELECT length FROM lines) ) 
      AND number < 500;

(It's just an example, not a real code)

How does PostgreSQL react when the result from the MIN has a number > 500 ? Is he then going after the second MIN or what happens ?

4

What do you mean by line = length?

I guess what you mean is that your subquery will find the id of the shortest line. Then you ask in the outer query for a line with that id and some number less than 500. If the shortest line then have a a number that is more than 500 you will get nothing back.

EDIT

Something like this should work if I understand you right.

SELECT DISTINCT ON (id) id , geom
FROM lines_table 
WHERE some_number < 500 
ORDER BY id, ST_Length(geom);
  • thank you! and how can I achieve this? Select the line with the highest length, but with other conditions (like the number <500, for example) – user28088 Mar 26 '14 at 17:40

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