Yongke Bill Yu Yongke Bill Yu - 24 days ago 5
JSON Question

How to JSON_MODIFY on Array of Array?

My strucutre look like this

Declare @layout NVARCHAR(MAX) = N'
{
"Sections": [
{
"SectionName":"Section1",
"SectionOrder":1,
"Renders":[
{
"RenderName":"Render1",
"RenderOrder":1,
"Fields":[
{
"FieldName":"Field1",
"FieldData":"Data1"
},
{
"FieldName":"Field2",
"FieldData":"Data2"
}
]
},
{
"RenderName":"Render2",
"RenderOrder":2,
"Fields":[
{
"FieldName":"Field1",
"FieldData":"Data1"
},
{
"FieldName":"Field2",
"FieldData":"Data2"
}
]
}
]
},
{
"SectionName":"Section2",
"SectionOrder":2,
"Renders":[
{
"RenderName":"Render1",
"RenderOrder":1,
"Fields":[
{
"FieldName":"Field1",
"FieldData":"Data1"
}
]
},
{
"RenderName":"Render2",
"RenderOrder":2,
"Fields":[
{
"FieldName":"Field1",
"FieldData":"Data1"
},
{
"FieldName":"Field2",
"FieldData":"Data2"
}
]
}
]
}
]
}
'


What I would like to do is to do this:

update FieldData = 'DataUpdated'
where FieldName = 'Field2'
and RenderName = 'Render'
and SectionName = 'Section1'


How would I do this using JSON_MODIFY?

I can GET the data using the following query:

SELECT SectionName, SectionOrder, RenderName, RenderOrder, FieldName, FieldData FROM (
SELECT SectionName, SectionOrder, RenderName, RenderOrder, Fields FROM (
select SectionName, SectionOrder, Renders
from OPENJSON(@layout,'$.Sections')
WITH (
SectionName nvarchar(MAX) '$.SectionName',
SectionOrder nvarchar(MAX) '$.SectionOrder',
Renders nvarchar(MAX) '$.Renders' as JSON
)
) as Sections
CROSS APPLY OPENJSON(Renders,'$')
WITH (
RenderName nvarchar(MAX) '$.RenderName',
RenderOrder nvarchar(MAX) '$.RenderOrder',
Fields nvarchar(MAX) '$.Fields' as JSON
)
) as Renders
CROSS APPLY OPENJSON(Fields,'$')
WITH (
FieldName nvarchar(MAX) '$.FieldName',
FieldData nvarchar(MAX) '$.FieldData'
)

Answer

This is not as straightforward as one might hope. I was surprised that there seems to be no simple way to query the full path of an item in a JSON structure.

JSON_MODIFY can only accept array indicies when targetting a member of an array, so most of the work here goes into generating the indexes for each nested array member. It appears that the [key] column can only be generated when using OPENJSON without a WITH clause, so I couldn't reuse your query.

Additionally, JSON_MODIFY will only accept a string literal for the JSON path, so the update has to be carried out using dynamic SQL.

(Please note that this solution assumes that you want to update a specific RenderName e.g. 'Render1' - the question is unclear on this point.)

DECLARE @path nvarchar(2048)

SELECT @path = FORMATMESSAGE('SET @layout = JSON_MODIFY(@layout, ''$.Sections[%s].Renders[%s].Fields[%s].FieldData'', @newValue)' ,sectionindex, renderindex, [key])
FROM
(
    SELECT sectionindex, sectionName, b.[key] as renderindex, b.[value] AS bvalue, JSON_VALUE([Value], '$.RenderName') AS renderName
    FROM
        (SELECT [key] AS sectionindex, [Value] AS avalue, JSON_VALUE([Value], '$.SectionName') AS sectionName
        FROM OPENJSON(@layout, '$.Sections') ) AS sections
        CROSS APPLY OPENJSON(sections.avalue, '$.Renders') AS b
    ) AS renders
    CROSS APPLY OPENJSON(renders.bvalue,'$.Fields'
) AS d
WHERE JSON_VALUE([Value], '$.FieldName') = 'Field2' 
AND RenderName = 'Render1'
AND SectionName = 'Section1'

-- execute the update; this has to happen in dynamic SQL because the JSON_MODIFY path has to be a literal value, and cannot be a variable
EXEC sp_executeSQL @path, N'@layout nvarchar(max) OUTPUT, @newValue nvarchar(max)', @layout = @layout OUTPUT, @newValue = 'DateUpdated'

--check the results
SELECT sectionindex, sectionName, renderindex, rendername, [key] AS fieldindex, JSON_VALUE([Value], '$.FieldName') AS FieldName, JSON_VALUE([Value], '$.FieldData') AS FieldName
FROM
(
    SELECT sectionindex, sectionName, b.[key] AS renderindex, b.[value] AS bvalue, JSON_VALUE([Value], '$.RenderName') AS renderName
    FROM
        (SELECT [key] as sectionindex, [Value] as avalue, JSON_VALUE([Value], '$.SectionName') AS sectionName
        FROM OPENJSON(@layout, '$.Sections') ) AS sections
        CROSS APPLY OPENJSON(sections.avalue, '$.Renders') AS b
    ) AS renders
    CROSS APPLY OPENJSON(renders.bvalue,'$.Fields'
) AS d
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