MS Sql Server OPENJSON 功能有问题答案

【问题标题】：Having trouble with MS Sql Server OPENJSON featureMS Sql Server OPENJSON 功能有问题
【发布时间】：2021-09-30 19:54:26
【问题描述】：

我为这个问题在下面创建了一个 sql 测试脚本。

 IF OBJECT_ID('tempdb..#temp') IS NOT NULL
    DROP TABLE #temp;

CREATE TABLE #temp
(
    Id INT NOT NULL PRIMARY KEY
  , Attributes NVARCHAR(MAX) NULL
);

INSERT INTO #temp (Id, Attributes)
VALUES (1, '[{"Name":"Step","Value":"A"},{"Name":"State","Value":"Active"}]');
INSERT INTO #temp (Id, Attributes)
VALUES (2, '[{"Name":"Step","Value":"B"},{"Name":"State","Value":"Inactive"}]');
INSERT INTO #temp (Id, Attributes)
VALUES (3, '[{"Name":"State","Value":"Active"}]');
INSERT INTO #temp (Id, Attributes)
VALUES (4, '[{"Name":"Step","Value":"D"}]');

SELECT
    t.Id
  , t.Attributes
  , stepname.Value AS [Step]
  , statename.Value AS [State]
FROM #temp t
    CROSS APPLY
    OPENJSON(t.Attributes)
    WITH
    (
        Name NVARCHAR(MAX) '$.Name'
      , Value NVARCHAR(MAX) '$.Value'
    ) AS stepname
    CROSS APPLY
    OPENJSON(t.Attributes)
    WITH
    (
        Name NVARCHAR(MAX) '$.Name'
      , Value NVARCHAR(MAX) '$.Value'
    ) AS statename
WHERE 1 = 1
      --AND (stepname.Name = statename.Name)     -- A
      --AND                                      -- B
      --(                                        -- B
      --    stepname.Name IS NULL                -- B
      --    OR stepname.Name = 'Step'            -- B
      --)                                        -- B
      --AND                                      -- B
      --(                                        -- B
      --    statename.Name IS NULL               -- B
      --    OR statename.Name = 'State'          -- B
      --);                                       -- B

按原样运行此脚本会产生以下输出：

Id	Attributes	Step	State
1	[{"Name":"Step","Value":"A"},{"Name":"State","Value":"Active"}]	A	A
1	[{"Name":"Step","Value":"A"},{"Name":"State","Value":"Active"}]	A	Active
1	[{"Name":"Step","Value":"A"},{"Name":"State","Value":"Active"}]	Active	A
1	[{"Name":"Step","Value":"A"},{"Name":"State","Value":"Active"}]	Active	Active
2	[{"Name":"Step","Value":"B"},{"Name":"State","Value":"Inactive"}]	B	B
2	[{"Name":"Step","Value":"B"},{"Name":"State","Value":"Inactive"}]	B	Inactive
2	[{"Name":"Step","Value":"B"},{"Name":"State","Value":"Inactive"}]	Inactive	B
2	[{"Name":"Step","Value":"B"},{"Name":"State","Value":"Inactive"}]	Inactive	Inactive
3	[{"Name":"State","Value":"Active"}]	Active	Active
4	[{"Name":"Step","Value":"D"}]	D	D

我希望在输出中看到的只有 4 行，每个数据行一个。

Id	Attributes	Step	State
1	[{"Name":"Step","Value":"A"},{"Name":"State","Value":"Active"}]	A	Active
2	[{"Name":"Step","Value":"B"},{"Name":"State","Value":"Inactive"}]	B	Inactive
3	[{"Name":"State","Value":"Active"}]		Active
4	[{"Name":"Step","Value":"D"}]	D

我在示例中留下了一些注释代码，以查看我尝试过的事情的类型，但都无济于事。用“--A”取消注释 where 语句让我更接近，但不是完全。我确信在 where 子句中取消注释最后带有“-- B”的语句会给我想要的东西，但事实并非如此。关于如何做到这一点的任何想法？

我最初只有 1 个 OPENJSON 块但没有成功，所以我认为也许有 2 个 OPENJSON 块，一个用于步骤，一个用于状态会有所帮助，但仍然无法获取包含的数据行 3 和 4因为这些行中的每一行都缺少 2 个 JSON 值之一。

非常感谢您的帮助！

【问题讨论】：

标签： sql-server open-json

【解决方案1】：

可以使用条件聚合：

SELECT
    t.Id
  , t.Attributes
  , [Step] = MAX(CASE WHEN stepname.Name = 'Step' THEN stepname.Value END)
  , [State] = MAX(CASE WHEN statename.Name = 'State' THEN statename.Value END) 
FROM #temp t
CROSS APPLY OPENJSON(t.Attributes) WITH (
        Name NVARCHAR(MAX) '$.Name'
      , Value NVARCHAR(MAX) '$.Value'
    ) AS stepname
CROSS APPLY OPENJSON(t.Attributes) WITH (
        Name NVARCHAR(MAX) '$.Name'
      , Value NVARCHAR(MAX) '$.Value'
    ) AS statename
GROUP BY t.Id, t.Attributes
ORDER BY t.Id;

db<>fiddle demo

【讨论】：