插入更新中丢失的行

Question

我想编写一个查询，如果我使用变量，它看起来像（伪代码）

records = SELECT * FROM table_1 WHERE id = x

numberOfRowsUpdated = UPDATE table_2 SET column_1 = y WHERE id = record1.id

INSERT INTO table2 (columns) (records.id, records.name, ...) where records exists and numberOfRowsUpdated == 0

目前，我有类似的东西，但语法似乎无效。有人能够提供有关在

WHERE

子句中包含更新声明的任何帮助吗？

WITH records AS (SELECT id, tx_id FROM table_1 WHERE id = NEW.id)
INSERT INTO table_2 (id,txn_id)
SELECT records.id, records.txn_id)
FROM records
WHERE EXISTS (SELECT 1 FROM records)
AND (UPDATE table_2 SET has_txn = true WHERE id in (records.id) = 0)

我让它以一种不稳定的方式工作，我想改进它，这样我就不会多次查询记录

WITH records AS (SELECT * FROM table_1 WHERE txn_id = NEW.id),
numberOfRowsUpdated AS (
    UPDATE table_2 SET has_txn = true WHERE id in (SELECT id FROM 
    table_1 WHERE txn_id = NEW.id) RETURNING 1
)
INSERT INTO balance_activity_outbox (
 id,
 ...
) SELECT (
 records.id,
 ...
 )
FROM records, numberOfRowsUpdated
WHERE EXISTS (SELECT 1 FROM records)
AND (select count(*) from numberOfRowsUpdated) = 0;

Answer 1

就像 Laurenz 已经怀疑的那样，看起来 UPSERT 可以做到：

INSERT INTO balance_activity_outbox (id, ...)
SELECT id, ...
FROM   table_1
WHERE  txn_id = NEW.id
ON     CONFLICT (id) DO UPDATE
SET    has_txn = true
WHERE  has_txn IS NOT TRUE;

需要

balance_activity_outbox(id)

上的唯一约束/索引或主键。

我添加了最后一个

WHERE has_txn IS NOT TRUE

来取消空更新。仅当这种情况发生时才有用。参见：

• 我如何（或可以）在多列上选择不同的？