How can I use json values as columns in a query SQL? - json

Question

I just want to receive a json data and use it's fields as a table column for another queries.
I'm trying to make the value in the key "nameProperty" into a column in a table, and the value of the keys "newValue"fill the rows of that column.
For example:
i get a json file like this
{
"operation":{
"ID":"ABC",
"KinshipDescription":"--"
},
"fields":[
{
"property":{
"nameProperty":"ID",
"oldValue":"",
"newValue":"123456",
"confirmed":"false",
"labelProperty":"ID",
"oldValueDescription":"",
"newValueDescription":"123456"
}
},
{
"property":{
"nameProperty":"Name",
"oldValue":"",
"newValue":"John",
"confirmed":"false",
"labelProperty":"Name",
"oldValueDescription":"",
"newValueDescription":"John"
}
}
]
}
I want to extract the objects on the list "fields", but i only can make them an row for key, and another row for values like the script below makes.
DECLARE #jsonObj NVARCHAR(MAX)
--Set a result in
SET #jsonObj = (select JSON_Query(data, '$.fields') from table where id = 'ABC')
select * from openjson(#jsonObj)
with (Property nvarchar(255) '$.property.nameProperty',
newValue nvarchar(50) '$.property.newValue')
and I have no idea how I can do this
the results of this script is something like this
ID 123456
Name John
and the results that i want to see is
ID Name --column name, not a row
123456 John

Answer 1

The quickest (thought-wise, not necessarily performance) way I can come up with on this is using dynamic SQL. In fact, I'm pretty certain you'll have to use it.
Here's an example that can get you moving. You can run this in SSMS.
DECLARE #json NVARCHAR(MAX) =
'{
"operation":{
"ID":"ABC",
"KinshipDescription":"--"
},
"fields":[
{
"property":{
"nameProperty":"ID",
"oldValue":"",
"newValue":"123456",
"confirmed":"false",
"labelProperty":"ID",
"oldValueDescription":"",
"newValueDescription":"123456"
}
},
{
"property":{
"nameProperty":"Name",
"oldValue":"",
"newValue":"John",
"confirmed":"false",
"labelProperty":"Name",
"oldValueDescription":"",
"newValueDescription":"John"
}
}
]
}';
-- Variable to hold the column/values.
DECLARE #cols VARCHAR(MAX) = '';
-- Generate the column/value pairs.
SELECT
#cols = #cols
+ CASE WHEN ( LEN( #cols ) > 0 ) THEN ', ' ELSE '' END -- add comma if needed.
+ '''' + Properties.newValue + ''' AS [' + Properties.nameProperty + '] '
FROM OPENJSON( #json, '$.fields' ) WITH (
property NVARCHAR(MAX) '$.property' AS JSON
)
CROSS APPLY (
SELECT * FROM OPENJSON( property ) WITH (
nameProperty VARCHAR(50) '$.nameProperty',
oldValue VARCHAR(50) '$.oldValue',
newValue VARCHAR(50) '$.newValue',
confirmed VARCHAR(50) '$.confirmed',
labelProperty VARCHAR(50) '$.labelProperty',
oldValueDescription VARCHAR(50) '$.oldValueDescription',
newValueDescription VARCHAR(50) '$.newValueDescription'
)
) AS Properties;
-- Execute column/value pairs as dynamic SQL.
EXEC ( 'SELECT ' + #cols );
Which returns:
+--------+------+
| ID | Name |
+--------+------+
| 123456 | John |
+--------+------+
If you were to PRINT #cols you would see
'123456' AS [ID] , 'John' AS [Name]
A few quick notes:
Performance may vary.
Values are quoted but can be CAST if needed.
Included all 'property' fields in CROSS APPLY for example. Only specify what is needed.
Note the use of NVARCHAR when using AS JSON
May want to consider OUTER APPLY if there's potential for no 'property' present.