如何在事务中获取SELECT语句的结果? [英] How to get the result of SELECT statement inside a transaction?

问题描述

我无法通过 PostgreSQL 文档、网络甚至 StackOverflow 获得有关这个简单问题的信息......我一定不明白这里的一些重要内容.

I can't get information of that simple question over the PostgreSQL documentation, over the Web or even here on StackOverflow... I must not understand something essential here.

我正在 PostgreSQL 中做一个简单的 SELECT/UPDATE 事务:

I am making a simple SELECT/UPDATE transaction in PostgreSQL:

START TRANSACTION;
SELECT "column" FROM "table" WHERE "criterion" = 'value' AND "activated" = true;
UPDATE "table" SET "activated" = false WHERE "criterion" = 'value';
COMMIT

基本上，当列的 activated 状态为 true 时，我需要获取该列的值，然后将其停用.PostgreSQL 告诉我有 1 行结果已被取消

Basically, I need to get the value of a column when its activated state is true and then deactivate it. PostgreSQL tells me that there was a 1 row result that has been cancelled

如果我执行以下操作(基本上是没有 UPDATE 语句的相同事务)，也会发生同样的情况:

The same happens if I do the following (basically the same transaction without the UPDATE statement):

START TRANSACTION;
SELECT "column" FROM "table" WHERE "criterion" = 'value' AND "activated" = true;
COMMIT

我对交易有什么不了解?任何 SELECT 输出都不能从交易块中取出吗?

What don't I understand about transactions? Can't any SELECT output get out of a transaction block?

推荐答案

这将从更新的行中返回所有列"的值:

This will return all "column"'s values from the updated rows:

UPDATE "table" SET "activated" = false WHERE "criterion" = 'value' AND "activated" = true
returning "column";

与交易无关.

returning 将返回值，就像发出了 select 一样:

returning will return the values as if a select was issued:

insert into foo (ticket, row, archived) values (3,7,true) returning *;
 ticket | row | archived 
--------+-----+----------
      3 |   7 | t

<小时>

update foo
set archived = true
where not archived
returning *;
 ticket | row | archived 
--------+-----+----------
      2 |   5 | t

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