查询 json 类型字符串 Postgres

Question

我的数据库中有一个带有 json 结构的文本列。 Postgres v.10

它可能看起来像这样：

{"pe_cd":"07","me_cd":"006","mf":"4.0","mfm":"4.0","pot":null,"earliestDate":[{"date":"2019-07-01","_destroy":false},{"date":"2020-01-01","_destroy":""}],"earliestDate2":null,"leavingDate":null}

如果 earlyDate2 = null 那么我需要进行更新查询并用最早日期 [] 的第一个日期填充它。在这种情况下 2019-07-01

在这种情况下的目标应该是：

{"pe_cd":"07","me_cd":"006","mf":"4.0","mfm":"4.0","pot":null,"earliestDate":[{"date":"2019-07-01","_destroy":false},{"date":"2020-01-01","_destroy":""}],"earliestDate2":"2019-07-01","leavingDate":null} 

我该如何编写这个更新查询？

Fiddle

Answer 1

要查询您的 json 类型字符串，您可以这样做：

`SELECT * FROM yourtable
WHERE json_like_column::JSON->'earliestDate' 为空

`

:: 会将您的字符串转换为 JSON 并且 -> 将从您的 json 中获取 'eraliestDate' 字段。您还可以使用 ->> 将该字段的值转换为字符串。

Answer 2

这是我为你想出的：

WITH null_dates AS
( -- Find the records with a NULL earliestDate2 and expand the dates stored
    SELECT id, (jsonb_array_elements((attr::JSONB)->'earliestDate')->>'date')::DATE as d
      FROM test
     WHERE (attr::JSONB)->>'earliestDate2' IS NULL
)
UPDATE test t
   SET attr = ((attr::JSONB)||jsonb_build_object('earliestDate2', sub.edate))::TEXT
  FROM
     ( -- Get the min date per ID from CTE (null_dates)
         SELECT id
              , MIN(d) AS edate
           FROM null_dates
          GROUP BY id
     ) sub
 WHERE t.id = sub.id
;

Here 是一个展示它的小提琴。