Question

我有两个表T_SUBJECTS（subject_id，date_of_birth）和T_ADMISSIONS（visit_id，subject_id，date_of_admission，age）。我想用入院时的年龄更新年龄栏。我编写了更新查询并获得＆＃34;单行子查询返回多行＆＃34;。我理解错误，但认为where exists子句将解决问题。以下是查询。

UPDATE
  t_admissions
SET
  t_admissions.age =
  (
    SELECT
      TRUNC(months_between(t_admissions.date_of_admission,
      t_subjects.date_of_birth)/12)
    FROM
      t_admissions,
      t_subjects
    WHERE
      t_admissions.subject_id           = t_subjects.subject_id
    AND t_admissions.age = 0
    AND t_admissions.date_of_admission IS NOT NULL
    AND t_subjects.date_of_birth       IS NOT NULL
  )
WHERE
   EXISTS
  (
    SELECT
      1
    FROM
      t_admissions, t_subjects
    WHERE
      t_admissions.subject_id = t_subjects.subject_id
  );

Answer 1

问题是SET子句中的子查询返回多行拥有WHERE子句只会过滤哪些记录得到更新而没有其他内容此外，您的where子句将始终返回true或始终返回false。

您应该了解如何正确执行相关更新：
https://stackoverflow.com/a/7031405/477563

Answer 2

根据上述链接的建议，我需要相关更新。见下面的答案。

UPDATE
  (
    SELECT
      t_admissions.visit_id,
      t_admissions.date_of_admission doa,
      t_admissions.age age,
      t_subjects.date_of_birth dob
    FROM
      t_admissions,
      t_subjects
    WHERE
      t_admissions.subject_id = t_subjects.subject_id
    AND t_admissions.age      = 0
    AND t_admissions.date_of_admission IS NOT NULL
    AND t_subjects.date_of_birth IS NOT NULL
  )
SET
  age = TRUNC(months_between(doa,dob)/12);

子查询在更新期间返回多行

2 个答案: