sql - if else 带参数的 postgres 过程

Question

我有这样的查询

CREATE  FUNCTION getVisitChartByClient(date_from DATE, date_to DATE, statusname TEXT, club_uuid TEXT) 

RETURNS TABLE(date date, entries bigint) AS $$
DECLARE
   ids UUID[];
BEGIN
ids = string_to_array(club_uuid,',');

        RETURN QUERY  SELECT d.date, count(v.id) AS entries
            FROM (SELECT  i::date AS date
                  FROM generate_series(date_from, date_to, '1 day'::interval) i
                 ) d 
                 LEFT  JOIN (
                     SELECT v.created_at, v.id FROM visit AS v 
                     LEFT JOIN club AS c ON v.club_id= c.id
                     AND status = statusname
                     AND c.uuid = ANY(ids)
                     GROUP BY v.id
                     ) AS v

                 ON d.date = v.created_at::date
            GROUP BY d.date
            Order By d.date ASC;


END;
$$ LANGUAGE plpgsql;

但有时我不想传递状态名称或俱乐部 ID，如何在查询中使用 IF ELSE 语句，或者如何创建查询然后执行？

Answer 1

尝试:

AND status = coalesce(statusname,status)

和

AND case when club_uuid is null then then true else c.uuid = ANY(ids) end

所以:

    RETURN QUERY  SELECT d.date, count(v.id) AS entries
        FROM (SELECT  i::date AS date
              FROM generate_series(date_from, date_to, '1 day'::interval) i
             ) d 
             LEFT  JOIN (
                 SELECT v.created_at, v.id FROM visit AS v 
                 LEFT JOIN club AS c ON v.club_id= c.id
                 AND status = coalesce(statusname,status)
                 AND case when club_uuid is null then then true else c.uuid = ANY(ids) end
                 GROUP BY v.id
                 ) AS v

             ON d.date = v.created_at::date
        GROUP BY d.date
        Order By d.date ASC;

当然，您需要将 NULL 传递给函数而不是“正常”值