在公用表表达式中使用更新

Question

以下是CTE，它是较大查询的一部分。 我正在尝试一些简单的事情：用“ 2016-10”更新或替换“ 2016-11”或“ 2016-12”值的所有记录。

查询在UPDATE时发生错误。 这里是否有替代方法可以使此查询正常工作？

with q (month, cobrand, members) as
(select date_trunc('month',optimized_transaction_date), cobrand_id, 
count(distinct unique_mem_id)
from yi_fourmpanel.card_panel
Where (cobrand_id = '10001372' or cobrand_id = '10005640' or cobrand_id = '10005244') 
group by 1,2)

UPDATE q
SET members = dc
FROM (SELECT cobrand, members dc
      FROM q
      WHERE month = '2016-10') x
WHERE q.cobrand = x.cobrand
AND month IN ('2016-11', '2016-12')

Answer 1

如果您不想更改表数据，请不要使用UPDATE 。

要实现您想要的功能，请编写类似于以下内容的主查询：

WITH q(month, cobrand, members) AS (...)
SELECT
   month,
   cobrand,
   CASE WHEN month IN ('2016-11', '2016-12')
        THEN (SELECT members
              FROM q q1
              WHERE q1.month = '2016-10')
        ELSE members
   END
FROM q;