Question

我有一个包含列的表：

microservice_id
transport_id
is_default
...

和一个唯一键（microservice_id，transport_id）我已经尝试了查询

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

主要思想是在更新之前删除所有冲突行，但DELETE子查询不能正常工作。我该如何解决？

[42601]错误：语法错误在或附近＆＃34; FROM＆＃34;

靠近DELETE

Answer 1

我会尝试重构声明：

数据：

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

像你一样：

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...

重构：

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

如果冲突，请在更新前删除行

1 个答案: