Calculating age based on month

If I am calculating age based on "date" using this query

select * 
from tblregistrations
WHERE  YEAR('20140701') - YEAR(DOB)
        - ( CASE
               WHEN MONTH(DOB) > MONTH('20140701')
                 OR ( MONTH(DOB) = MONTH('20140701')
                    AND DAY(DOB) > DAY('20140701')
                    )
               THEN 1
               ELSE 0
             END )  < 18

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How can I calculate based on "month" only?  Thanks for helping this novice sql person.
al4629740Asked:
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PortletPaulEE Topic AdvisorCommented:
please provide an example of what you mean by "month only"

is the DOB "month only"?
are you still comparing to the constant '20140701'?
an example would really help
al4629740Author Commented:
No, the new constant will be the month

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Scott PletcherSenior DBACommented:
If you want to see if a person is less than a certain age, you can just calculate the "controlling date", and then test for the DOB < that.  Something like this:

select *
from tblregistrations
WHERE  
    DOB < DATEADD(YEAR, -18, '20140701')
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al4629740Author Commented:
No, I just want to calculate their age based on current MONTH and DOB
Scott PletcherSenior DBACommented:
DATEDIFF(MONTH, DOB, GETDATE()) / 12

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al4629740Author Commented:
So I can basically stick whatever date I am comparing to in the GETDATE() section?

For example:

DATEDIFF(MONTH, DOB, GETDATE()) / 12
or
DATEDIFF(MONTH, DOB, '12/1/2014') / 12
or
DATEDIFF(MONTH, DOB, variable) / 12
PortletPaulEE Topic AdvisorCommented:
So "current month" can be treated as "1st of" the current month, and the calculation method remains the same.

declare @datum as date
set @datum = (select DATEADD(dd, - (DAY(getdate()) - 1), cast(getdate() as date) ) )

select * 
from tblregistrations
WHERE  YEAR(@datum) - YEAR(DOB)
        - ( CASE
               WHEN MONTH(DOB) > MONTH(@datum)
                 OR ( MONTH(DOB) = MONTH(@datum)
                    AND DAY(DOB) > DAY(@datum)
                    )
               THEN 1
               ELSE 0
             END )  < 18

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line 2 above calculates "1st day of current month"
Scott PletcherSenior DBACommented:
Yep, that should be it, if all you're worried about is the month of the dob.
al4629740Author Commented:
Yes, it would be comparing the month of DOB to month of whatever I specify
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