OPENJSON – using an explicit schema. The WITH clause.

G’day,

Previously, we have looked at using OPENJSON to gain knowledge about the JSON document that we have presented to the function.

A bit like this

SELECT
*
FROM
OPENJSON
(
'
  {
    "configuration_id": 101,
    "Configuration name": "recovery interval (min)",
    "Value": 0,
    "minimum": 0,
    "maximum": 32767,
    "value_in_use": 0,
    "description": "Maximum recovery interval in minutes",
    "is_dynamic": true,
    "is_advanced": true
  }
'
)

Notice that we didn’t request any columns in the SELECT statement, but we got three columns back

• Key
• value
• type

That’s great metadata information – but what if we wanted the actual values from the JSON.

Well, the statement above used OPENJSON with the default schema – which is basically no column list defined. If we want to define a list then we need to use a WITH clause that defines an EXPLICIT schema – like so

SELECT
 *
FROM
OPENJSON
(
'
  {
    "configuration_id": 101,
    "Configuration name": "recovery interval (min)",
    "Value": 0,
    "minimum": 0,
    "maximum": 32767,
    "value_in_use": 0,
    "description": "Maximum recovery interval in minutes",
    "is_dynamic": true,
    "is_advanced": true
  }
'
)
WITH
(
     [configuration_id]     INT 
    ,[Configuration name]   NVARCHAR(35)
    ,[Value]                NVARCHAR(200)
    ,[minimum]              NVARCHAR(200)
    ,[maximum]              NVARCHAR(200)
    ,[value_in_use]         NVARCHAR(200)
    ,[description]          NVARCHAR(200)
    ,[is_dynamic]           BIT
    ,[is_advanced]          BIT
);
GO

You might also notice that the names in the WITH clause match those in the JSON document – We can also add these as a column list to the SELECT statement, rather than using SELECT *

Notice also that if we ask for a value in the WITH clause that does not appear in the JSON document (maybe because of a typo) then we simply get a NULL returned in the SELECT list.

Notice here that the name of the first column is incorrect. So we get a null in the resultset.

SELECT
*
FROM
OPENJSON
(
'
  {
    "configuration_id": 101,
    "Configuration name": "recovery interval (min)",
    "Value": 0,
    "minimum": 0,
    "maximum": 32767,
    "value_in_use": 0,
    "description": "Maximum recovery interval in minutes",
    "is_dynamic": true,
    "is_advanced": true
  }
'
)
WITH
(
     [configuration_if]     INT 
    ,[Configuration name]   NVARCHAR(35)
    ,[Value]                NVARCHAR(200)
    ,[minimum]              NVARCHAR(200)
    ,[maximum]              NVARCHAR(200)
    ,[value_in_use]         NVARCHAR(200)
    ,[description]          NVARCHAR(200)
    ,[is_dynamic]           BIT
    ,[is_advanced]          BIT
);
GO

This is perhaps one reason that we should include an explicit column list in the SELECT statement

SELECT
     [configuration_id]
    ,[Configuration name] 
    ,[Value] 
    ,[minimum]
    ,[maximum] 
    ,[value_in_use]
    ,[description]
    ,[is_dynamic]
    ,[is_advanced]
FROM
OPENJSON
(
'
  {
    "configuration_id": 101,
    "Configuration name": "recovery interval (min)",
    "Value": 0,
    "minimum": 0,
    "maximum": 32767,
    "value_in_use": 0,
    "description": "Maximum recovery interval in minutes",
    "is_dynamic": true,
    "is_advanced": true
  }
'
)
WITH
(
     [configuration_id]     INT 
    ,[Configuration name]   NVARCHAR(35)
    ,[Value]                NVARCHAR(200)
    ,[minimum]              NVARCHAR(200)
    ,[maximum]              NVARCHAR(200)
    ,[value_in_use]         NVARCHAR(200)
    ,[description]          NVARCHAR(200)
    ,[is_dynamic]           BIT
    ,[is_advanced]          BIT
);
GO

And we pretty much see exactly what we had before.

Next up is some more useful tips about OPENJSON

Have a great day

Cheers

Marty

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OPENJSON – using an explicit schema. The WITH clause