json_blob.py

# -----------------------------------------------------------------------------
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#
# This software is dual-licensed to you under the Universal Permissive License
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# the following applies:
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# Licensed under the Apache License, Version 2.0 (the "License");
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# See the License for the specific language governing permissions and
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# -----------------------------------------------------------------------------
# json_blob.py
#
# Demonstrates how to use a BLOB as a JSON column store.
#
# Note: Oracle Database 12c lets JSON be stored in VARCHAR2 or LOB columns.
#       With Oracle Database 21c using the new JSON type is recommended
#       instead, see json_direct.py
#
# Documentation:
#     python-oracledb: https://oracledb.readthedocs.io/en/latest/user_guide/json_data_type.html
#     Oracle Database: https://www.oracle.com/pls/topic/lookup?ctx=dblatest&id=ADJSN
# -----------------------------------------------------------------------------

import json
import sys

import oracledb
import sample_env

# determine whether to use python-oracledb thin mode or thick mode
if not sample_env.get_is_thin():
    oracledb.init_oracle_client(lib_dir=sample_env.get_oracle_client())

connection = oracledb.connect(
    user=sample_env.get_main_user(),
    password=sample_env.get_main_password(),
    dsn=sample_env.get_connect_string(),
    params=sample_env.get_connect_params(),
)

if not connection.thin:
    client_version = oracledb.clientversion()[0]
db_version = int(connection.version.split(".")[0])

# Minimum database version is 12
if db_version < 12:
    sys.exit("This example requires Oracle Database 12.1.0.2 or later")

# Insert JSON data
with connection.cursor() as cursor:
    data = dict(name="Rod", dept="Sales", location="Germany")
    inssql = "insert into CustomersAsBlob values (:1, :2)"

    if (connection.thin or client_version >= 21) and db_version >= 21:
        # Take advantage of direct binding
        cursor.setinputsizes(None, oracledb.DB_TYPE_JSON)
        cursor.execute(inssql, [1, data])
    else:
        # Insert the data as a JSON string
        cursor.execute(inssql, [1, json.dumps(data)])

# Select JSON data
with connection.cursor() as cursor:
    sql = "select c.json_data from CustomersAsBlob c"
    for (j,) in cursor.execute(sql):
        print(j)

    # Using JSON_VALUE to extract a value from a JSON column

    sql = """select json_value(json_data, '$.location')
             from CustomersAsBlob
             offset 0 rows fetch next 1 rows only"""
    for r in cursor.execute(sql):
        print(r)

    # Using dot-notation to extract a value from a JSON  (BLOB storage) column

    sql = """select c.json_data.location
             from CustomersAsBlob c
             offset 0 rows fetch next 1 rows only"""
    for (j,) in cursor.execute(sql):
        print(j)

    # Using JSON_OBJECT to extract relational data as JSON

    sql = """select json_object('key' is d.dummy) dummy
             from dual d"""
    for r in cursor.execute(sql):
        print(r)

    # Using JSON_ARRAYAGG to extract a whole relational table as JSON

    oracledb.defaults.fetch_lobs = False
    sql = """select json_arrayagg(
                        json_object('key' is c.id,
                                    'name' is c.json_data)
                        returning clob)
             from CustomersAsBlob c"""
    for r in cursor.execute(sql):
        print(r)