sql - 我可以更新 cte 吗？

Question

我尝试使用 CTE

WITH cte as ( 
     SELECT myFieldName, 
            row_number() over (order by gps_device_id) as rn
     FROM tracker.gps_devices
) 
UPDATE cte
SET cte.myFieldName = CASE WHEN cte.rn % 3  = 0  THEN '0'
                           WHEN cte.rn % 3  = 1  THEN '1'
                           WHEN cte.rn % 3  = 2  THEN '2'
                       END

但是出现如下错误。

ERROR: relation "cte" does not exist

看起来我可以在 WITH 之后执行 INSERT 和 DELETE 但 UPDATE 只能在 cte 内部，是吗正确的？我确定我做了类似的事情，但可能在不同的数据库中。

https://www.postgresql.org/docs/9.6/static/queries-with.html

所以我就此结束，即使工作非常困惑，有什么建议吗？

UPDATE tracker.gps_devices g
SET g.myFieldName = CASE WHEN t.rn % 3  = 0  THEN '0'
                         WHEN t.rn % 3  = 1  THEN '1'
                         WHEN t.rn % 3  = 2  THEN '2'
                    END
FROM (SELECT gps_device_id,
             myFieldName,
             row_number() over (order by gps_device_id) as rn
      FROM tracker.gps_devices) as t
WHERE g.gps_device_id = t.gps_device_id

Answer 1

您可以使用 cte 进行更新，例如(假设 id 是主键):

with cte as ( 
    select 
        id, 
        my_field_name, 
        row_number() over (order by gps_device_id) as rn
    from gps_devices
) 
update gps_devices
set my_field_name = (rn % 3)::text
from cte
where gps_devices.id = cte.id;

您可以插入、更新或删除表( View )的行，而不是查询的结果集。