Oracle SQL : JSON_TABLE ; Get sized of Array

Question

I would like to know if there is a way i could get the size of the array of a specific node in a JSON data.

As an example, below is the JSON.

For the node 'Phone' there are two items. I would like to know the size of this node. My objective is to parse the Java Array to a Java Array. If i am not aware of the size of the array i would not be able to parse.

Essentially i would like to get the value "2".

{"PONumber"              : 1600,
      "Reference"             : "ABULL-20140421",
       "Requestor"            : "Alexis Bull",
       "User"                 : "ABULL",
       "CostCenter"           : "A50",
       "ShippingInstructions" : {"name"   : "Alexis Bull",
                                 "Address": {"street"   : "200 Sporting Green",
                                              "city"    : "South San Francisco",
                                              "state"   : "CA",
                                              "zipCode" : 99236,
                                              "country" : "United States of America"},
                                 "Phone" : [{"type" : "Office", "number" : "909-555-7307"},
                                            {"type" : "Mobile", "number" : "415-555-1234"}]},
       "Special Instructions" : null,
       "AllowPartialShipment" : true,
       "LineItems" : [{"ItemNumber" : 1,
                       "Part" : {"Description" : "One Magic Christmas",
                                 "UnitPrice"   : 19.95,
                                 "UPCCode"     : 13131092899},
                       "Quantity" : 9.0},
                      {"ItemNumber" : 2,
                       "Part" : {"Description" : "Lethal Weapon",
                                 "UnitPrice"   : 19.95,
                                 "UPCCode"     : 85391628927},
                       "Quantity" : 5.0}]}

As an alternative, Using the below code i would get that data :

SELECT jt.phones
FROM j_purchaseorder,
JSON_TABLE(po_document, '$.ShippingInstructions'
COLUMNS
  (phones VARCHAR2(100) FORMAT JSON PATH '$.Phone')) AS jt;

however if i use

SELECT jt.phones
FROM j_purchaseorder,
JSON_TABLE(po_document, '$'
COLUMNS
  (ShippingInstructions VARCHAR2(100) FORMAT JSON PATH '$.ShippingInstructions')) AS jt;

i am getting the value as null. So how can i get the entire ShippingInstructions in a single value.

For representation , i have mentioned 100, but tried 1000 as well and still the same problem. — Asjad Azeez
– Asjad Azeez, Commented May 21, 2021 at 10:55

MT0 · Accepted Answer · 2021-05-24 13:37:52Z

For the node 'Phone' there are two items. I would like to know the size of this node.

Essentially i would like to get the value "2".

From this question and this question, you can use:

SELECT jt.phones
FROM   j_purchaseorder,
       JSON_TABLE(
         po_document,
         '$.ShippingInstructions'
         COLUMNS (
           phones VARCHAR2(100) FORMAT JSON WITH WRAPPER PATH '$.Phone.size()'
         )
       ) AS jt;

Which outputs:

PHONES

[2]

If you do not want the array wrapper then you can pass the return value through JSON_VALUE:

SELECT JSON_VALUE(jt.phones, '$[0]') AS phones
FROM   j_purchaseorder,
       JSON_TABLE(
         po_document,
         '$.ShippingInstructions'
         COLUMNS (
           phones VARCHAR2(100) FORMAT JSON WITH WRAPPER PATH '$.Phone.size()'
         )
       ) AS jt;

Which outputs:

PHONES

2

If you are Oracle 19c and your column is defined with an IS JSON check constraint then you can simplify the query to:

SELECT j.po_document."ShippingInstructions"."Phone".size() phones
FROM j_purchaseorder j;

Which outputs:

PHONES

2

If you are using an early Oracle version that does not support the size() function then you can get all rows and use COUNT:

SELECT COUNT(*) AS phones
FROM   j_purchaseorder,
       JSON_TABLE(
         po_document,
         '$.ShippingInstructions.Phone[*]'
         COLUMNS (
           phones VARCHAR2(100) FORMAT JSON PATH '$'
         )
       ) AS jt;

Which outputs:

PHONES

2

db<>fiddle here

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