BigQuery 更新在 table 上合并多行

Question

我有以下内容：

Table A:

|uid|info|..
|123|null|..



Table B:
|uid|goodinfo|timestamp|
|123  |  3     |2019-12-12
|123  |  5     |2019-01-12
|234  |  11    |2019-10-12

当我尝试运行更新语句时，我总是得到 "UPDATE/MERGE must match at most one source row for each target row" 错误，因为在 Table B 中我得到多行并且我没有任何方法使连接更多具体比这个。

我试过：

UPDATE `Table A` a
SET info = (select goodinfo from `Table B` where uid=123
ORDER BY lastmodifieddate DESC
LIMIT 1) b
WHERE 
a.info IS NULL AND
a.user_id=123

-- 这种方法有效，但因为在 SubQuery 中我无法访问 Table A，所以我无法将其概括为：

SET info = (select goodinfo from `Table B` where uid=a.uid
ORDER BY lastmodifieddate DESC
LIMIT 1) b

-- 这会抛出一个错误，说他不知道 "a.uid" 是谁

然后我尝试使用来自 BigQuery 的合并：

MERGE `Table A` a 
USING (
  select goodinfo,uid from `Table B` 
  ORDER BY lastmodifieddate DESC
  LIMIT 1
) b
ON a.uid = b.uid 
WHEN MATCHED and a.info is null and DATE(a.timestamp) = "2019-12-12" THEN
  UPDATE SET a.info = b.goodinfo

-- 此查询实际上已成功完成，但由于我尚未找到的原因，未修改任何行

那我试过了:

UPDATE `Table A` a 
SET a.info = b.goodinfo
FROM `Table B` b
WHERE a.uid = b.uid
and DATE(a.timestamp) = "2019-12-12"
and a.info IS NULL
//here I get the same error and I cannot filter the data from Table B and get the same error

关于以通用方式更新数据并以某种方式过滤来自 Table B 的数据并在加入时仅从 goodinfo 获取值“3”的任何想法？

我也在考虑做一个:

WITH filtered_table_b(
  select uid, goodinfo from Table B
  ORDER BY lastmodifieddate DESC
  LIMIT 1
)

但这无济于事，因为我不知何故需要 select 每个用户的基于时间戳的最后一个 goodinfo

谢谢

Answer 1

这是标准 SQL 您可以使用：

WITH data AS (
select '123' as uid, 3 as goodinfo, DATE('2019-12-12') as timestamp union all
select '123' as uid, 5 as goodinfo, DATE('2019-01-12') as timestamp union all
select '234' as uid, 11 as goodinfo, DATE('2019-10-12') as timestamp 
),
filterData AS (
select uid, max(timestamp) maxTimestamp from data
group by uid
)

select data.uid, goodinfo, filterData.maxTimestamp as  maxTimestamp 
from data inner join filterData on data.uid = filterData.uid and data.timestamp = filterData.maxTimestamp

这是上面的输出：

BigQuery 更新在 table 上合并多行

BigQuery Update merge on table with multiple rows

inner-join

bigdata

jointable

google-bigquery