SQL Server calculating age from varchar date of birth

Question

The stored procedure is provided with @minAge and @maxAge varchar values.

The table contains DOB column as a varchar , now I need to select rows where where DOB (Age) falls between minimum and maximum age.

For instance @minAge = 12 and @maxAge = 40 , we have to first convert the DOB string into Current Age and then only select the rows which fall between (inclusive) of 12 and 40.

I have the following code in mind but that produces errors

SELECT * 
FROM tableName
WHERE
    FLOOR((CAST(GetDate() AS INTEGER) - CAST(DOB AS INTEGER)) / 365.25) AS Age
      BETWEEN CAST(@minage AS INT) AND CAST(@maxAge AS INT)

Answer 1

One way of calculating the age is this:

DATEDIFF(YY, CAST(dob AS DATETIME), GETDATE()) - CASE WHEN( (MONTH(CAST(dob AS DATETIME))*100 + DAY(CAST(dob AS DATETIME))) > (MONTH(GETDATE())*100 + DAY(GETDATE())) ) THEN 1 ELSE 0 END AS Age

where dob is the date of birth stored as varchar (in a way that can be cast to a datetime).

An example:

declare @people table(name varchar(20), dob varchar(10))
insert @people values ('adam', '1970-01-01')
insert @people values ('burt', '2002-01-13')
insert @people values ('dave', '1992-11-13')
insert @people values ('eric', '1973-11-13')

SELECT 
    name, 
    DATEDIFF(YY, CAST(dob AS DATETIME), GETDATE()) - CASE WHEN( (MONTH(dob)*100 + DAY(dob)) > (MONTH(GETDATE())*100 + DAY(GETDATE())) ) THEN 1 ELSE 0 END AS Age
FROM @people 
WHERE DATEDIFF(YY, dob, GETDATE()) - CASE WHEN( (MONTH(dob)*100 + DAY(dob)) > (MONTH(GETDATE())*100 + DAY(GETDATE())) ) THEN 1 ELSE 0 END
BETWEEN 12 AND 40

This would be the result:

name    Age
burt    12
dave    21
eric    40

This might not be the best way though, but it should work.