Google BigQuery 错误：UPDATE/MERGE 必须与每个目标行最多匹配一个源行

Posted 2023-03-25

【中文标题】Google BigQuery 错误：UPDATE/MERGE 必须与每个目标行最多匹配一个源行

【英文标题】：Google BigQuery Error: UPDATE/MERGE must match at most one source row for each target row

【发布时间】：2019-12-17 16:34:20

【问题描述】：

我正在尝试通过比较（即更改的值）来更新引用新表的旧表。

我的查询如下：

UPDATE CogencyData.AUM
SET BeginBalanceBase = T1.BeginBalanceBase
FROM Cogency_Temp.AUM T1
LEFT OUTER JOIN CogencyData.AUM T2
ON T1.FundLongName = T2.FundLongName
AND T1.PeriodDate = T2.PeriodDate
WHERE COALESCE(T1.BeginBalanceBase, 0) <> COALESCE(T2.BeginBalanceBase);

但我收到以下错误：

UPDATE/MERGE must match at most one source row for each target row

我相信代码在 mysql 中运行良好。我该如何解决这个问题？

【问题讨论】：

注释掉前两行 (UPDATE/SET) 并替换为 SELECT T1.BeginBalanceBase as T1BBB, T2.BeginBalanceBase as T2BBB。有结果吗？

@rtenha 是的。结果我得到了两个值 - 也许这就是查询被混淆的原因？如何有效地更新这两个值？

【参考方案1】：

这个查询会给你同样的错误：

CREATE OR REPLACE TABLE temp.users AS (
   SELECT "1" id, 3 total
   UNION ALL SELECT "2", 2 total
   UNION ALL SELECT "3", 4 total
   UNION ALL SELECT "4", 5 total
)
;

UPDATE temp.users T0
SET total = T1.total + T2.total
FROM temp.users T1
LEFT OUTER JOIN temp.users T2
ON T1.id = T2.id
WHERE 1>0

这个查询修复了错误：

CREATE OR REPLACE TABLE temp.users AS (
   SELECT "1" id, 3 total
   UNION ALL SELECT "2", 2 total
   UNION ALL SELECT "3", 4 total
   UNION ALL SELECT "4", 5 total
)
;

UPDATE temp.users T0
SET total = T1.total + T2.total
FROM temp.users T1
LEFT OUTER JOIN temp.users T2
ON T1.id = T2.id
WHERE 1>0
AND T0.id = T1.id

诀窍是什么：最后一个 WHERE 子句 T0.id = T1.id 确保正在更新的表中的每一行只获得一次更新。