Calculate age between current date and birthdate

Question

Hi,

 

I want to calcute the diffence between current date and the date a person is born in year.

Birthday is stored in a column with vachar(12).

 

I try this SQL statement:

 

SELECT CONVERT(DATETIME,LEFT(birthdate,8),120), DATEDIFF(YEAR,CONVERT(DATETIME,LEFT(birthdate,8),120),getdate()) as 'Age' from Person

 

The funny thing with this SQL is if a person is born 201809234247  (social security number) and the current date is 2019-02-22 the age result will be 1 year. This is not true - it should be 0.

 

Something is wrong with my SQL statement but what?