Q:

Data stored in two separate tables, how to select the right table

I have two Tables T1 and T2 in which, where in T1 contains column name 'Year' which saves year information and T2 contains column name as 'P_year' which saves year information.
In the Table T1, I saved some data for the years '2011,2012,2013,2014'. In the Table T2, I am saving the data for the years '2015,2016...and it goes on.
Now, I had developed a common webform to view the results, wherein I placed a dropdown for the year to choose all the years 2011,2012,2013,2014,2015...
And I am confused how to choose...like if the user has selected any particular year, How should I choose the right select statement with the right table...i.e.if the user has selected 2013,then I have to choose select statement related to table T1 and if the user has selected 2015, then I have to choose select statement related to table T2 ?
And if the user doesn't selects the year,How should I display all the data from both tables ?
if(year == "2011" !!year == "2012"!!year == "2013"!!year == "2014")
{
query1 = "select * from T1 where year ="Selected Year";
}
else if (year == "2015")
{
query2 = "select * from T2 where year ="2015";
}
else
{
query1 = "select * from T1 where year in('2011','2012','2013','2014');
query2 = "select * from T2 where year ="2015";
}

So,I can handle the execution in choosing the right query to execute if the user has selected any particular year. But issue rise up, if the user doesn't selects the year, I have to display the data from both tables executing both queries...like I have shown above in the last else statement.
So, Is there any way to write code in a optimized way. Note:- Right here, I am just showing up a single lined query statement,but in real it exists for 5 or 6 lines of select statement.
Anyone please help me out in this regard.
Thanking You.

A:

'2011,2012,2013,2014'
'2015,2016 and so on'

dropdownlist included all Years
convert dropdownlist.selectedValue to int
if(int < 2015)
    query1 
else
    query2

