因為公司Table有用partition按月切開，
所以想寫一個函數可以動態來讀資料，
大概是下面那樣，

CREATE OR REPLACE FUNCTION dynamic_push("month_yyyymm" text)
RETURNS TABLE(m_id text, m_date timestamp, is_read text) AS
$$
BEGIN
execute
'
select *
from
(
select m_id::text, m_date::timestamp senddate, is_read::text
from admin.push_'||month_yyyymm||'
where m_date between now()-8 and date(now())-1
)
union
(
select *
from
(
select m_id::text, m_date::timestamp senddate, is_read::text
from admin.push_'||(month_yyyymm::numeric-1)::text||'
where m_date between now()-8 and date(now())-1
)
)
';
END;
$$ LANGUAGE plpgsql;

select *
from dynamic_apppush(to_char(now(),'yyyymm')::text);

但想加判斷式進去，判斷同月即執行第一段，跨月再執行整串，
修改後如下，但是執行一直有Error，想求助大神問題大概出在哪呢？
(Error 一直發生在 ; 處)

CREATE OR REPLACE FUNCTION dynamic_push("month_yyyymm" text)
RETURNS TABLE(m_id text, m_date timestamp, is_read text) AS
$$
BEGIN
if to_char(now()-8,'yyyymm') = to_char(date(now())-1,'yyyymm') then
execute
'
select *
from
(
select m_id::text, m_date::timestamp senddate, is_read::text
from admin.push_'||month_yyyymm||'
where m_date between now()-8 and date(now())-1
)
';
else
execute
'
select *
from
(
select m_id::text, m_date::timestamp senddate, is_read::text
from admin.push_'||month_yyyymm||'
where m_date between now()-8 and date(now())-1
)
union
(
select *
from
(
select m_id::text, m_date::timestamp senddate, is_read::text
from admin.push_'||(month_yyyymm::numeric-1)::text||'
where m_date between now()-8 and date(now())-1
)
)
';
END IF;
END;
$$ LANGUAGE plpgsql;