hadoop - 在Shark Hive中创建连接两个现有表的表

Question

我有两个表oldTable和newTable，其内容为:
oldTable:

  key    value    volume
  ======================
  1      abc      10000
  2      def      5000

newTable:

  key    value    volume
  ======================
  1      abc      2000
  2      def      3000
  3      xyz      7000

我想创建一个新表，该表汇总两个表中的volume。也就是说，新表格应包含以下内容:
joined_table:

  key    value    volume
  ======================
  1      abc      12000
  2      def      8000
  3      xyz      7000

我尝试使用以下语句，但没有结果:

CREATE TABLE joined_table AS
SELECT key, value, volume
FROM (
    SELECT IF(oldTable.key != NULL, oldTable.key, newTable.key) AS key,
        IF(oldTable.value != NULL, oldTable.value, newTable.value) AS value,
        IF(oldTable.volume AND newTable.volume, oldTable.volume + newTable.volume,
    IF(oldTable.volume != NULL, oldTable.volume, newTable.volume)) AS volume
    FROM(
        SELECT oldTable.key, oldTable.value, oldTable.volume, newTable.key, newTable.value, newTable.volume
        FROM newTable FULL OUTER JOIN oldTable ON newTable.key = oldTable.key
    )alias
)anotherAlias;

但这给我说了Query returned non-zero code: 10, cause: FAILED: Error in semantic analysis: Ambiguous column reference key一个错误。

我尝试在上述查询中更改joined_table中的列名，但这给了我同样的错误。如何实现这一目标有帮助吗？

另外，有什么方法可以将结果覆盖到现有表中，比如oldTable而不是创建这个新表？

Answer 1

您在查询中使用的单词key是保留关键字。这可能是解析器抛出歧义错误的原因。您可以使用反勾号来避免解析器将其读取为保留文字。

CREATE TABLE joined_table AS
SELECT `key`, value, volume
FROM (
SELECT IF(oldTable.`key` != NULL, oldTable.`key`, newTable.`key`) AS `key`,
    IF(oldTable.value != NULL, oldTable.value, newTable.value) AS value,
    IF(oldTable.volume AND newTable.volume, oldTable.volume + newTable.volume,
IF(oldTable.volume != NULL, oldTable.volume, newTable.volume)) AS volume
FROM(
    SELECT oldTable.`key`, oldTable.value, oldTable.volume, newTable.`key`, newTable.value, newTable,volume
    FROM newTable FULL OUTER JOIN oldTable ON newTable.`key` = oldTable.`key`;
)alias
)anotherAlias;