如何从Oracles JSON CLOB类型的JSON数组中选择特定元素

Question

我有一个CLOB列,其中包含以下数据(为了解决此问题而简化)

{
    "notUsed": [],
    "stock": [
        {
            "name": "eggs",
            "value": "in stock"
        },
        {
            "name": "milk",
            "value": "out of stock"
        }
    ]
}

我想避免必须选择整个对象并以编程方式解析以获取我想要的数据.理想情况下,我想利用Oracle JSON路径功能来实现这一目标.

我想得到"value",在哪里"name" = "eggs"

我试过以下,但得到了一个[99999][40442] ORA-40442: JSON path expression syntax error.我已通过评估程序运行上面的示例JSON和JSON路径,并返回所需的结果,这让我觉得Oracle拥有自己的JSONPath解释

SELECT
  json_query(
                 '{"notUsed":[],"stock":[{"name":"eggs","value":"in stock"}, {"name":"milk","value":"out of stock"}]}',
                 '$.stock[?(@.name=="eggs")]' )
FROM dual;

我也尝试过使用Dot Notation,但是还没有找到一个例子,它涵盖了将where子句添加到数组的属性中.

select
  myTable.id,
  myTable.JSON_COLUMN.stock    -- how to get array element here?
from MY_TABLE myTable
where j.id = 46

版:

SELECT * FROM V$VERSION

Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
"CORE   12.1.0.2.0  Production"

Answer 1

根据手册,JSON_path_expression仅支持一些基本语法:

JSON_path_expression :: =

object_step :: =

array_step :: =

另一种方法是使用JSON_TABLE将JSON转换为关系表,然后对列进行投影和过滤.

select value
from json_table(
    '{
        "notUsed": [],
        "stock": [
            {
                "name": "eggs",
                "value": "in stock"
            },
            {
                "name": "milk",
                "value": "out of stock"
            }
        ]
    }',
    '$.stock[*]'
    columns
    (
        name varchar2(100 char) path '$.name',
        value varchar2(100 char) path '$.value'
    )
)
where name = 'eggs'

结果:

VALUE
-----
in stock