Retrieving A Piece Of Datalogged Equipment By Most Recent Time

The TSQL below all works except the bolded part at the end. I'm want to grab only the most recently logged piece of equipment not the most recent and all past ones as well which is what I've got doing minus the bolded part below. But I don't know how to say get this Equipment ID etc and only the most recently logged one to find its present location. The bolded part below is just there to show what I want it to do I know you can use an aggregate in a where clause. So in the first table listed tblRdrLog there is a column Time that I want to do this on so a.Time. I don't want to display a.Time just reference.

String dbsql = " SELECT a.EquipmentID " +
" , f.Subcategory " +
" , c.Area " +
" , d.Room " +
" FROM tblRdrLog a " +
" JOIN tblRdrInfo b ON a.ReaderID = b.ReaderID " +
" JOIN tblRdrArea c ON b.AreaID = c.AreaID " +
" JOIN tblRdrRm d ON b.RoomID = d.RoomID " +
" JOIN tblEquipInfo e ON a.EquipmentID = e.EquipmentID " +
" JOIN tblEquipSubcat f ON e.SubcategoryID = f.SubcategoryID " +
" WHERE a.EquipmentID IN (SELECT a.EquipmentID " +
" FROM tblEquipInfo a " +
" JOIN tblEquipCat b ON a.CategoryID = b.CategoryID " +
" JOIN tblEquipSubcat c ON a.SubcategoryID = c.SubcategoryID " +
" LEFT OUTER JOIN tblEquipMake d ON a.MakeID = d.MakeID " +
" LEFT OUTER JOIN tblEquipModel e ON a.ModelID = e.ModelID " +
" JOIN tblStatus f ON a.StatusID = f.StatusID " +
" WHERE b.CategoryID = '" + this.ddlCategory.SelectedValue.ToString() + "' ";

if (!"".Equals(this.ddlSubcategory.SelectedValue.ToString()))
dbsql += " AND c.SubcategoryID = '" + this.ddlSubcategory.SelectedValue.ToString() + "' ";

#region Advanced Search Criteria

// Check whether advanced search submitted
if (adv)
{
if (!"".Equals(this.tbSerialNo.Text.ToString()))
dbsql += " AND a.SerialNo = '" + this.tbSerialNo.Text.ToString() + "' ";
if (!"".Equals(this.ddlMake.SelectedValue.ToString()))
dbsql += " AND d.MakeID = '" + this.ddlMake.SelectedValue.ToString() + "' ";
if (!"".Equals(this.ddlModel.SelectedValue.ToString()))
dbsql += " AND e.ModelID = '" + this.ddlModel.SelectedValue.ToString() + "' ";
if (!"".Equals(this.ddlStatus.SelectedValue.ToString()))
dbsql += " AND f.StatusID = '" + this.ddlStatus.SelectedValue.ToString() + "' ";
}

#endregion

dbsql += " ) " +
" AND a.Time = max(a.Time) " +
"";