Hola Verifique la consulta a continuación.
--DROP TABLE patient
CREATE TABLE patient(PatName varchar(100),DOB date, Age varchar(100))
INSERT INTO patient
VALUES('a','06/02/1947',NULL),('b','07/10/1947',NULL),('c','12/21/1982',NULL)
;WITH CTE(PatName,DOB,years,months,days) AS
(SELECT PatName,DOB,DATEDIFF(yy,DOB,getdate()),DATEDIFF(mm,DOB,getdate()),DATEDIFF(dd,DOB,getdate()) FROM patient)
--SELECT * FROM CTE
SELECT PatName,DOB,
CAST(months/12 as varchar(5))+' Years'+CAST((months % 12) as varchar(5))+' month/s '+CAST(CASE WHEN DATEADD(MM,(months % 12),DATEADD(YY,(months/12),DOB)) <= GETDATE() then DATEDIFF(dd,DATEADD(MM,(months % 12),DATEADD(YY,(months/12),DOB)),GETDATE()) ELSE DAY(getdate()) END as varchar(5))+' days' as Age
FROM CTE
