Re: Can't use ORDER BY in subqueries

Hi, I have two tables: CREATE TABLE lines (ID INT, size INT, line GEOMETRY); CREATE TABLE polygons (ID INT, size INT, polygon GEOMETRY); The query I want to call is the following: SELECT COUNT(*) FROM POLYGONS one JOIN (SELECT LINE FROM LINES ORDER BY Length(line) DESC LIMIT 1) two ON "Intersect"(one.polygon, two.line) = TRUE; I tried out to create a function that replaces the use of the subquery: create function line_max() returns table (id integer) begin return select id from lines order by Length(line) desc limit 1; end; select count(*) From polygons one join lines two ON "Intersect"(one.polygon, two.line) = TRUE where two.id in (select id from line_max()); The query started without errors but it stops with the following error: HEAPalloc: Insufficient space for HEAP of 7200000000 bytes. Thanks Leo

On 05 Nov 2014, at 17:48, Stefan Manegold wrote:

Hi Leo,

could you give an SQL example of the very query you'd like to run but that MonetDB "rejects" due to order by and/or limit in a sub query?

Thanks!

Stefan

----- Original Message -----

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Hi,

I understand why Monetdb does’t support ORDER BY in subqueries.

An ORDER BY combined with a LIMIT does influence the size of the query result set. Is there a workaround to use such a query?

Here’s my use case: I’m working with the spatial extension and have a table filled with polygons. Now I want to know the ids of all polygons that intersect the polygon with the biggest area.

Is there a chance to answer this use case with only one query?

Regards Leo

...

On 27 Oct 2014, at 19:02, Martin Kersten wrote:

Hi

ORDER BY (and LIMIT/OFFSET for that matter) only control the overall shape of the query result set. Hence, they are indeed not supported within subqueries in MonetDB.

See thread https://www.monetdb.org/pipermail/users-list/2013-October/006861.html

regards, Martin

On 27/10/14 17:57, Kotschenreuther, Leo wrote:

...

Hi all,

I tried to use some more complex queries, they contained subqueries. I will shortly desrcibe the situation:

I have two tables (e.g. test and foo) and want to join them. Furthermore I want to preselect a subset of one of the two tables by adding some conditions (e.g. order the records by attribute c and only choosing the biggest one). A query could look like the this:

*sql>select * from test join (select * from foo order by c limit 1);* * * The result I receive is the following:

*syntax error, unexpected ORDER, expecting INTERSECT or EXCEPT or UNION or ')' in: "select * from test join (select * from foo order**”* * * On the other hand, I can run the subquery without the main query and I receive a valid result.

Is there a possibility to use subqueries with an ORDER BY statement without separating them into two independent queries?

Regards Leo

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