Question

使用Postgres 11，如何转换此JSON对象（以文本索引和整数作为值）

{"a":{"col1":1,"col2":2,"col3":3}
,"b":{"col1":4,"col2":5,"col3":6}
,"c":{"col1":7,"col2":8,"col3":9}}

到类似这样的记录集：

r_id | col1 | col2 | col3
-------------------------
   a |    1 |    2 |    3
   b |    4 |    5 |    6
   c |    7 |    8 |    9

Answer 1

SELECT key AS r_id, value->>'col1' AS col1, value->>'col2' AS col2, value->>'col3' AS col3
FROM JSON_EACH('{"a":{"col1":1,"col2":2,"col3":3},"b":{"col1":4,"col2":5,"col3":6},"c":{"col1":7,"col2":8,"col3":9}}');

Answer 2

Your solution对于三个值列似乎足够好。

列越多，json_populate_record()会缩短语法并使其速度更快。但是，它基于模板行类型，而您没有。您可以通过创建一个临时表（在会话内部可见，直到会话结束）轻松提供它：

CREATE TEMP TABLE t1(col1 int, col2 int, col3 int);

SELECT key AS r_id, (json_populate_record(null::t1, value)).*
FROM json_each('{"a":{"col1":1,"col2":2,"col3":3}
               , "b":{"col1":4,"col2":5,"col3":6}
               , "c":{"col1":7,"col2":8,"col3":9}}')

如果您的JSON文档是一个记录数组，则可以使用json_populate_recordset()：

CREATE TEMP TABLE t2(r_id text, col1 int, col2 int, col3 int);

SELECT *
FROM   json_populate_recordset(null::t2
             , '[{"r_id":"a","col1":1,"col2":2,"col3":3}
               , {"r_id":"b","col1":4,"col2":5,"col3":6}
               , {"r_id":"c","col1":7,"col2":8,"col3":9}]');

将JSON对象转换为记录集？

2 个答案: