Database

public void WhatsInside() {
   Debug.WriteLine(this.CommandText);
   foreach (OleDbParameter param in this.Parameters) {
      Debug.WriteLine(param.DbType + param.value + ...);
   }
   other possible info...
}

select id, newname,oldname
from emp e1
left outer join emp e2 on e2.id = e1.id
and e2.datemodified = (select max(datemodified) from emp e3 where e3.id = e2.id
and e3.datemodified < e2.datemodified)

select id, newname,oldnamefrom emp e1left outer join emp e2 on e2.id = e1.idand e2.datemodified = (select max(datemodified) from emp e3 where e3.id = e2.idand e3.datemodified < e1.datemodified)

SELECT AGE_CATEGORY, SUM(MALES) AS MALES, SUM(FEMALES) AS FEMALES, 
convert(float,(sum(males) + sum(females))) * 100 / (SELECT SUM(MALES) + SUM(FEMALES) FROM AGE_CATS) as PCent
FROM AGE_CATS GROUP BY AGE_CATEGORY

DECLARE @tot float
select @tot = SUM(MALES) + SUM(FEMALES) FROM AGE_CATS 

SELECT AGE_CATEGORY, SUM(MALES) AS MALES, SUM(FEMALES) AS FEMALES ,
convert(float,(sum(males) + sum(females))) * 100 / @tot as Pcent
FROM AGE_CATS GROUP BY AGE_CATEGORY