JSON_DATAGUIDE

Syntax

Description of the illustration json_dataguide.eps

Purpose

The aggregate function JSON_DATAGUIDE computes the data guide of a set of JSON data. The data guide is returned as a CLOB which can be in either flat or hierarchical format depending on the passing format parameter.

expr

expr is a SQL expression that evaluates to a JSON object or a JSON array. It can also be a JSON column in a table.

format options

Use the format options to specify the format of the data guide that will be returned. It must be one of the following values:

• dbms_json.format_flat for a flat format.

• dbms_json.format_hierarchical for a hierarchical format.

If the parameter is the absent, the default is dbms_json.format_flat.

flag options

flag can have the following values:

• Specify DBMS_JSON.PRETTY to improve readability of the returned data guide with appropriate indentation.

• Specify DBMS_JSON.GEOJSON for the data guide to auto detect the GeoJSON type. The corresponding view column created by the data guide will be of sdo_geometry type.

• Specify DBMS_JSON.GATHER_STATS for the data guide to collect statistical information. The data guide report generated with DBMS_JSON.GATHER_STATS has a new field o:sample_size, in addition to all of the other statistical fields that you get with DBMS_JSON.get_index_dataguide .

• All three values DBMS_JSON.PRETTY, DBMS_JSON.GEOJSON, and DBMS_JSON.GATHER_STATS can be combined with a plus sign. For example, DBMS_JSON.GEOJSON+DBMS_JSON.PRETTY, or DBMS_JSON.GEOJSON+DBMS_JSON.PRETTY+DBMS_JSON.GATHER_STATS.

See Also:

JSON Data Guide

Examples

The following example uses the j_purchaseorder table, which is created in "Creating a Table That Contains a JSON Document: Example". This table contains a column of JSON data called po_document. This example returns a flat data guide for each year group.

SELECT EXTRACT(YEAR FROM date_loaded) YEAR,
       JSON_DATAGUIDE(po_document) "DATA GUIDE"
  FROM j_purchaseorder
  GROUP BY extract(YEAR FROM date_loaded)
  ORDER BY extract(YEAR FROM date_loaded) DESC;


YEAR DATA GUIDE
---- ------------------------------------------
2016 [
       {
         "o:path" : "$.PO_ID",
         "type" : "number",
         "o:length" : 4
       },
       {
         "o:path" : "$.PO_Ref",
         "type" : "string",
         "o:length" : 16
       },
       {
         "o:path" : "$.PO_Items",
         "type" : "array",
         "o:length" : 64
       },
       {
         "o:path" : "$.PO_Items.Part_No",
         "type" : "number",
         "o:length" : 16
       },
       {
         "o:path" : "$.PO_Items.Item_Quantity",
         "type" : "number",
         "o:length" : 2
       }
     ]
. . .