Oracle 18c

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WITH AGRI_INCOME(accreage, sellingprice, attr1, crop, attr2 ) AS
(
 SELECT '2', '2500', '81400', 'Khariff', 'AGRICULTURE_INCOME' FROM dual
), CASH_FLOW(Coapp1,Coapp2,Coapp3,Lease_Land,Total_Land,Land_under_cultivation,Land_Holding) AS
(
 SELECT '1', '2', null, '2', null, '4', '5' FROM dual 
), AGRI_INCOME_JS AS
(
SELECT JSON_OBJECT( 'Agriculture_Expenses' value
                    JSON_ARRAYAGG(JSON_OBJECT ('Acreage12'         value accreage,
                                               'Farmer_projected'  value sellingprice,
                                               'Projected_Expense' value attr1,
                                               'Pattern1'          value crop
                                               )
                                  )
                    ) AS JS2
  FROM AGRI_INCOME
 WHERE ATTR2 = 'AGRICULTURE_INCOME'
), CASH_FLOW_JS AS
(
SELECT JSON_OBJECT('Cash_Flow_Form' value
                   JSON_ARRAYAGG(JSON_OBJECT('Agri_Coapp1' value coapp1,
                                             'Agri_Coapp2' value coapp2,
                                             'Agri_Coapp3' value coapp3,
                                             'Lease_Land' value  lease_land,
                                             'Total_Land' value  Total_Land,
                                             'Land_under_cultivation1' value Land_under_cultivation,
                                             'App_agr_lan' value Land_Holding
                                             )
                                 )            
                                 
                  ) AS JS1
  FROM CASH_FLOW
)
SELECT JSON_MERGEPATCH(JS1,JS2) AS "Result JSON"
  FROM CASH_FLOW_JS
 CROSS JOIN AGRI_INCOME_JS

Result JSON
{"Cash_Flow_Form":[{"Agri_Coapp1":"1","Agri_Coapp2":"2","Agri_Coapp3":null,"Lease_Land":"2","Total_Land":null,"Land_under_cultivation1":"4","App_agr_lan":"5"}],"Agriculture_Expenses":[{"Acreage12":"2","Farmer_projected":"2500","Projected_Expense":"81400","Pattern1":"Khariff"}]}

WITH AGRI_INCOME(accreage, sellingprice, attr1, crop, attr2 ) AS
(
 SELECT '2', '2500', '81400', 'Khariff', 'AGRICULTURE_INCOME' FROM dual
), CASH_FLOW(Coapp1,Coapp2,Coapp3,Lease_Land,Total_Land,Land_under_cultivation,Land_Holding) AS
(
 SELECT '1', '2', null, '2', null, '4', '5' FROM dual 
), AGRI_INCOME_JS AS
(
SELECT JSON_OBJECT( 'Agriculture_Expenses' value
                    JSON_ARRAYAGG(JSON_OBJECT ('Acreage12'         value accreage,
                                               'Farmer_projected'  value sellingprice,
                                               'Projected_Expense' value attr1,
                                               'Pattern1'          value crop
                                               )
                                  )
                    ) AS JS2
  FROM AGRI_INCOME
 WHERE ATTR2 = 'AGRICULTURE_INCOME'
), CASH_FLOW_JS AS
(
SELECT JSON_OBJECT('Cash_Flow_Form' value
                   JSON_ARRAYAGG(JSON_OBJECT('Agri_Coapp1' value coapp1,
                                             'Agri_Coapp2' value coapp2,
                                             'Agri_Coapp3' value coapp3,
                                             'Lease_Land' value  lease_land,
                                             'Total_Land' value  Total_Land,
                                             'Land_under_cultivation1' value Land_under_cultivation,
                                             'App_agr_lan' value Land_Holding
                                             )
                                 )            
                                 
                  ) AS JS1
  FROM CASH_FLOW
), JS(JS) AS
(
SELECT JS1 FROM CASH_FLOW_JS
UNION ALL 
SELECT JS2 FROM AGRI_INCOME_JS)
SELECT REPLACE(REPLACE(REPLACE(REPLACE(JSON_ARRAYAGG(JS),'\'),'["'),'"]'),'}","{',',') 
   AS "Result JSON"
  FROM JS

Result JSON
{"Cash_Flow_Form":[{"Agri_Coapp1":"1","Agri_Coapp2":"2","Agri_Coapp3":null,"Lease_Land":"2","Total_Land":null,"Land_under_cultivation1":"4","App_agr_lan":"5"}],"Agriculture_Expenses":[{"Acreage12":"2","Farmer_projected":"2500","Projected_Expense":"81400","Pattern1":"Khariff"}]}