Oracle PL/SQL-基于最大列数插入值

我试图将数据（产品、时间戳）插入表a、B和C中的表xyz中，主键为产品。这三个表都有一个timestamp列和其他列。我想插入包含这三个表（A、B和C）的乘积和最大时间戳的行。

根据Sentine的评论更新了：

尝试以下操作（语法未验证）：

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如果表xyz中已经存在product，则不指定要执行的操作，因此假设它不存在，可以使用如下查询：

Insert into XYZ(Product, Timestamp)
Select Product, max(timestamp)
  from (select product, timestamp from a union all
        select product, timestamp from b union all
        select product, timestamp from c)
 group by product

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您可以尝试以下方法：

INSERT INTO xyz
  ( product, timestamp )
SELECT MAX(product) KEEP ( DENSE_RANK FIRST ORDER BY timestamp DESC ) AS product
     , MAX(timestamp)
  FROM a
 UNION ALL
SELECT MAX(product) KEEP ( DENSE_RANK FIRST ORDER BY timestamp DESC ) AS product
     , MAX(timestamp)
  FROM b
 UNION ALL
SELECT MAX(product) KEEP ( DENSE_RANK FIRST ORDER BY timestamp DESC ) AS product
     , MAX(timestamp)
  FROM c;

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希望这能有所帮助。

您应该展示您迄今为止所做的尝试，以及它不起作用的原因。。不要把你的问题抛在脑后，指望别人会为你提问。你可以添加更多的细节，比如所需结果的示例；源表数据示例您不能像这样将子查询中的4列插入目标表中的两列。@Sentinel，rRe thinkingHe希望获得所有表的最大时间戳，即每个表（A、B和C）的最大值为3条记录。否OP声明Product是表XYZ的主键，因此只有一条Product记录，和所有三个表（A、B和C）的最大时间戳。请删除-1。

INSERT INTO xyz
  ( product, timestamp )
SELECT MAX(product) KEEP ( DENSE_RANK FIRST ORDER BY timestamp DESC ) AS product
     , MAX(timestamp)
  FROM a
 UNION ALL
SELECT MAX(product) KEEP ( DENSE_RANK FIRST ORDER BY timestamp DESC ) AS product
     , MAX(timestamp)
  FROM b
 UNION ALL
SELECT MAX(product) KEEP ( DENSE_RANK FIRST ORDER BY timestamp DESC ) AS product
     , MAX(timestamp)
  FROM c;