java - 更新子查询中的数据

Question

我有两个表:

• PERSON带列person_id和total
• DATA带列data_a , data_b , data_c ，和data_person_id

每个“人”在 DATA 中可以有零个或多个条目- 您的标准一对多关系。 PERSON有一个total即 DATA 中的值之和的列。目前 total 之间存在一些差异。以及 DATA 中的实际条目哪里DATA是正确的，但是 total是错误的。

这是我用来查找差异的查询:

SELECT
  person_id
FROM PERSON JOIN (
  SELECT
    data_person_id,
    SUM( data_a + data_b + data_c ) as data_total
  FROM
    DATA
  GROUP BY
    data_person_id
  ) x ON data_person_id = person_id
WHERE
  person_total != data_total

我计划通过 Hibernate 作为查询来执行此操作，其中后端将是 Postgres 9.x。

我试图理解/修复的错误查询是:

UPDATE
  ONLY PERSON
SET
  total = data_info.calc_total
FROM (
  SELECT
    SUM( data_a + data_b + data_c ) as calc_total
  FROM
    DATA
  WHERE
    DATA.data_person_id = person_id
  GROUP BY
    DATA.data_person_id
) as data_info
WHERE
  PERSON.person_id IN (
    SELECT
      data_person_id
    FROM PERSON JOIN (
      SELECT
        data_person_id,
        SUM( data_a + data_b + data_c ) as data_total
      FROM
        DATA
      GROUP BY
        data_person_id
      ) x ON person_id = data_person_id
    WHERE
      total != data_total
  )

现在，它不会运行，因为 WHERE DATA.data_person_id = person_id 。但如果我把它去掉，就会使用错误的值。

以下似乎有效，但我很困惑为什么:

UPDATE
  ONLY PERSON
SET
  total = data_info.calc_total
FROM 
  PERSON P JOIN (
    SELECT
      data_person_id,
      SUM( data_a + data_b + data_c ) as calc_total
    FROM
      DATA
    WHERE
      DATA.data_person_id = person_id
    GROUP BY
      DATA.data_person_id
  ) as data_info ON P.person_id = data_person_id
WHERE
  PERSON.person_id IN (
    SELECT
      data_person_id
    FROM PERSON JOIN (
      SELECT
        data_person_id,
        SUM( data_a + data_b + data_c ) as data_total
      FROM
        DATA
      GROUP BY
        data_person_id
      ) x ON person_id = data_person_id
    WHERE
      total != data_total
  )

我相信我的问题在于我对 doc 的误解(我猜是关于自连接的部分)。

此外，任何改进此查询的方法都值得赞赏!

Answer 1

看来您的查询太复杂了。任务应该很简单:

UPDATE person p
SET    total = d.calc_total
FROM (
  SELECT data_person_id, sum(data_a + data_b + data_c) as calc_total
  FROM   data
  GROUP  BY 1
) d
WHERE  p.person_id = d.data_person_id
AND    p.total IS DISTINCT FROM d.calc_total;

• 首先从 data 表中聚合 calc_total，按 data_person_id 分组。

• 然后在 UPDATE 的 FROM 子句中使用此子查询。

• 我使用 IS DISTINCT FROM 来确保覆盖 NULL 值，而实际上只更新会更改的行。
  如果所有涉及的列都定义为NOT NULL，则可以使用=。

-> sqlfiddle demo.