conditional Order By SQL statement for tokio postgres in Rust [duplicate] - postgresql

Question

How can i achieve dynamic order by column and sort direction in a postgresql function.
Here is what i have so far:
CREATE OR REPLACE FUNCTION get_urls_by_crawl_id(
p_account_id character varying(64),
p_crawl_id character varying(64),
p_sort_column character varying(30),
p_sort_direction character varying(30),
p_page integer,
p_total integer
)
RETURNS TABLE(id character varying(64), source_url text, http_status_code integer, ref_cnt integer) AS $BODY$
BEGIN
RETURN QUERY SELECT u.id, u.source_url, u.http_status_code, u.ref_cnt FROM url AS u
JOIN crawl AS c ON(u.crawl_id = c.id)
JOIN site AS s ON(c.site_id = s.id)
JOIN person AS p ON(s.person_id = p.id)
WHERE p.account_id = p_account_id AND u.crawl_id = p_crawl_id AND u.secured = 0
ORDER BY p_sort_column (CASE WHEN p_sort_direction = 'ASC' THEN ASC ELSE DESC END) LIMIT p_total OFFSET (p_page * p_total);
END;
$BODY$ LANGUAGE plpgsql;
the psql client returns this error:
ERROR: syntax error at or near "ASC"
LINE 16: ...t_column (CASE WHEN p_sort_direction = 'ASC' THEN ASC ELSE D...
I have tried multiple forms of the CASE statement but none seems to work.

Answer 1

Use two different order by keys:
ORDER BY (case when p_sort_direction = 'ASC' then p_sort_column end)
asc,
p_sort_column desc
LIMIT p_total OFFSET (p_page * p_total);
Note that you have another problem. p_sort_column is a string. You would need to use dynamic SQL to insert it into the code.
Alternatively, you can use a series of cases:
order by (case when p_sort_column = 'column1' and p_sort_direction = 'ASC' then column1 end) asc,
(case when p_sort_column = 'column1' and p_sort_direction = 'DESC' then column1 end) desc,
(case when p_sort_column = 'column2' and p_sort_direction = 'ASC' then column2 end) asc,
(case when p_sort_column = 'column2' and p_sort_direction = 'DESC' then column2 end) desc,
. . .