Question

我正在努力在PostgreSQL查询中声明变量。有人可以帮我解决下面的问题吗？

declare CampaignID val INT;
select CampaignID = 6
select
    result_code.description,
    count (*) as count
from 
    history
        left join result_code on result_code.result_code = history.result_code
where
    campaign_id = CampaignID
        and history.start_date_time between '2016-12-06 00:00:00' and '2016-12-06 23:00:00'
group by
    result_code.description

Answer 1

1）第一种方式（使用PL / pgSQL函数）：

CREATE OR REPLACE FUNCTION MY_SELECT_FUNC(CampaignID integer)
RETURNS TABLE(res_description character varying(255), res_count integer) AS
$BODY$
BEGIN

  for res_description, res_count
  in
  select
    result_code.description,
    count (*) as count
  from history
    left join result_code on result_code.result_code = history.result_code
  where campaign_id = CampaignID
    and history.start_date_time between '2016-12-06 00:00:00' and '2016-12-06 23:00:00'
  group by result_code.description
  loop
    return next;
  end loop;

END;$BODY$
LANGUAGE plpgsql VOLATILE;

然后你可以在sql中选择结果：

SELECT * from MY_SELECT_FUNC(6);

2）第二种方式（使用sql函数）：

CREATE TYPE MY_SELECT_FUNC_RES AS (res_description character varying(255), res_count integer);

CREATE OR REPLACE FUNCTION MY_SELECT_FUNC(CampaignID integer)
RETURNS SETOF MY_SELECT_FUNC_RES AS
$$
  select
    result_code.description,
    CAST(count(*) AS INTEGER)
  from history
    left join result_code on result_code.result_code = history.result_code
  where campaign_id = CampaignID
    and history.start_date_time between '2016-12-06 00:00:00' and '2016-12-06 23:00:00'
  group by result_code.description
$$
LANGUAGE SQL;

然后你可以在sql中选择结果：

SELECT * from MY_SELECT_FUNC(6);

如何在PostgreSQL查询中声明变量

1 个答案: