刪除行更新，如果衝突

microservice_id
transport_id
is_default
...

和唯一的密鑰（microservice_id， transport_id）我試過查詢

UPDATE microservices_transports 
SET 
    transport_id = :next, 
    username  = :username, 
    password  = :password, 
    is_default = COUNT((SELECT * 
        FROM 
         (DELETE FROM microservices_transports AS mt WHERE mt.transport_id = :NEXT AND mt.microservice_id = microservice_id RETURNING *) 
        WHERE is_default = TRUE 
        )) > 0 
WHERE 
transport_id = :prev

主要想法是在更新之前刪除所有衝突行，但DELETE子查詢將無法工作。我該如何解決它？

[42601] ERROR: syntax error at or near "FROM"

附近DELETE

來源

2017-10-05 Illorian

怎麼不工作？錯誤？ –

你會得到什麼錯誤？ –

* [42601]錯誤：在DELETE附近的「FROM」*附近出現語法錯誤，因爲我認爲 – Illorian

我想嘗試重構聲明：

數據：

t=# select * from a; 
i 
--- 
1 
(1 row)

水木清華喜歡你：

t=# begin; update a set i = (select count(*) from (delete from a returning *)); 
BEGIN 
ERROR: syntax error at or near "from" 
LINE 1: update a set i = (select count(*) from (delete from a return...

重構：

t=# with d as (delete from a where i = 1 returning *) 
, c as (select count(*) from d) 
update a set i = c.count from c; 
UPDATE 0

來源

2017-10-05 07:15:10

刪除行更新，如果衝突

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