casematch groupby

[Ahmed-elshorbagy]

i have DateTime birthdate column how can i group users by age like
from 15-20 20-30 40-50 50-60
using CaseMatch
is there abetter solution than custom select

DateTime now=DateTime.now();
   int today=DateTime(now.year,now.month,now.day).millisecondsSinceEpoch~/ 1000;
   int year =4383*2*60*60*groupAge;
   //  GROUP BY modyear
   return (customSelect(
"SELECT Count(id) as cnt,((?-birthdate)/?)*? as modyear FROM usersGROUP BY modyear;",
       variables: [Variable<int>(today), Variable<int>(year),Variable<int>(groupAge)],
       readsFrom: {users,}).map((QueryRow row) {
     return PatAge(
       id:row.read<int>('cnt'),
       age: row.read<int>('modyear'),
       
     );
   })).watch();
 }

thanks in advance