SQL OPENJSON 读取带有空/空数组的嵌套 JSON

Question

我有简单的 JSON 和嵌套数组，其中一些可能为空或为 null，并且由于 null 值，我无法获得整个结果行。

declare @json nvarchar(max)

set @json = '{"orders": [{
                "id": 1,
                "items": 
                [{
                    "sku": "abc",
                    "quantity": 1,
                    "price": 100,
                    "discount": 
                        [{
                            "amount": "10",
                            "amount_set": 
                                {
                                "shop": 
                                    {
                                    "total": "10",
                                    "currency_code": "EUR"
                                    },
                                "presentment": 
                                    {
                                    "total": "10",
                                    "currency_code": "EUR"
                                    }
                                }
                        }]
                }]
                },{
                "id": 2,
                "items": 
                [{
                    "sku": "def",
                    "quantity": 1,
                    "price": 111,
                    "discount": []
                }]
                }
        ] }'

SELECT cOrderID, cSKU, nQty, nPrice, nDiscount
FROM 
(
    OPENJSON(@json, '$.orders') 
    WITH (
        cOrderID NVARCHAR(20) '$.id',  
        Items NVARCHAR(MAX) '$.items' AS JSON
        )
    CROSS APPLY OPENJSON(Items,'$')
    WITH (
        cSKU NVARCHAR(30) '$.sku',  
        nQty DECIMAL(19,6) '$.quantity',
        nPrice FLOAT '$.price',
        Discount NVARCHAR(MAX) '$.discount' AS JSON
        )
    CROSS APPLY OPENJSON(Discount,'$')
    WITH (
        nDiscount DECIMAL(19,6) '$.amount'
        )
)

我得到这个结果：

cOrderID     cSKU          nQty          nPrice          nDiscount
------------ ------------- ------------- --------------- -----------------
1            abc           1.000000      100             10.000000

我期望得到这个结果：

cOrderID     cSKU          nQty          nPrice          nDiscount
------------ ------------- ------------- --------------- -----------------
1            abc           1.000000      100             10.000000
2            def           1.000000      111             null

如何显示带有空数组的行？

Answer 1

解决方案是在数组OUTER APPLY上Discount：

SELECT cOrderID, cSKU, nQty, nPrice, nDiscount
FROM 
(
OPENJSON(@json, '$.orders') 
WITH (
    cOrderID NVARCHAR(20) '$.id',  
    Items NVARCHAR(MAX) '$.items' AS JSON
    )
CROSS APPLY OPENJSON(Items,'$')
WITH (
    cSKU NVARCHAR(30) '$.sku',  
    nQty DECIMAL(19,6) '$.quantity',
    nPrice FLOAT '$.price',
    Discount NVARCHAR(MAX) '$.discount' AS JSON
    )
OUTER APPLY OPENJSON(Discount,'$')
WITH (
    nDiscount DECIMAL(19,6) '$.amount'
    )
)

结果完全符合预期：

cOrderID     cSKU          nQty          nPrice          nDiscount
------------ ------------- ------------- --------------- -----------------
1            abc           1.000000      100             10.000000
2            def           1.000000      111             null