How to Fetch doctype

I want to fetch the doctype. How do I do this? I want to add a separate column which will give doctype such as sales order,purchase order etc.The first line gives me error what query should be fired.I want to fetch doctype field and not doctype name. Please help i am new to ERP Next.

SELECT
AD.ref_doctype AS “Doctype:Link/User:120”,
AD.name AS “Doc#:Link/Doctype:120”,
AD.owner AS “Created By:Link/User:120”,
AD.modified AS “Modified On:Date:120”
FROM tabAddress AS AD
WHERE
DATEDIFF(now(),AD.modified) BETWEEN 1 AND 30
UNION ALL
SELECT
TR.name AS “Doc#:Link/Doctype:120”,
TR.owner AS “Created By:Link/User:120”,
TR.modified AS “Modified On:Date:120”
FROM tabTax Rule AS TR
WHERE
DATEDIFF(now(),TR.modified) BETWEEN 1 AND 30
UNION ALL
SELECT
IT.name AS “Doc#:Link/Doctype:120”,
IT.owner AS “Created By:Link/User:120”,
IT.modified AS “Modified On:Date:120”
FROM tabItem AS IT
WHERE
DATEDIFF(now(),IT.modified) BETWEEN 1 AND 30