How to compare in 2 data tables?

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I have 2 datatables.each of them has column "ID".I want to get those IDs that are present in both datatables.
How should i do it.
i also need to put the extracted rows in a new datatable.how do i do that?

Posted 12-Apr-12 2:55am

sapna62

Updated 12-Apr-12 3:16am

v2

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2 solutions

Solution 2

This is a walk which is effecient. If you use the foreach, as the tables get larger you increase the time by the square (O(x square)). This solution is linear (O(x)):

DataTable dt1 = new DataTable();
DataTable dt2 = new DataTable();
int c1 = 0;
int c2 = 0;

while (c1 < dt1.Rows.Count  && c2 < dt2.Rows.Count)
{
    if ((int)dt1.Rows[c1][0] == (int) dt1.Rows[c2][0])
    {
        //Match found
        c1++;
        c2++;
    }
    else if ((int)dt1.Rows[c1][0] > (int)dt1.Rows[c2][0])
    {
        //Missing row in dt1
        c2++;
    }
    else
    {
        //Missing row in dt2
        c1++;
    }
}

if (c1 < dt1.Rows.Count)
{
    //Missing rows at the end in dt2
}
if (c2 < dt2.Rows.Count)
{
    //Missing rows at the end in dt1
}

If you want to have the results in a table then:

dt3.Rows.Add(dt1.Rows[c1]);

Where dt3 is another table you have defined.

Posted 12-Apr-12 5:24am

Clifford Nelson

Updated 12-Apr-12 5:52am

v4

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Nilesh Patil Kolhapur · Accepted Answer · 2012-04-12T03:04:00

hey,

u get common ids like following

DataTable dt = new DataTable();
dt.Columns.Add("ID");
dt.Rows.Add(1);
dt.Rows.Add(2);
dt.Rows.Add(3);
dt.Rows.Add(4);
DataTable dt1 = new DataTable();
dt1.Columns.Add("ID");

dt1.Rows.Add(1);
dt1.Rows.Add(2);
dt1.Rows.Add(3);

foreach (DataRow dr in dt.Rows)
{
foreach (DataRow dr1 in dt1.Rows)
{
if (dr[0].ToString() == dr1[0].ToString())
Response.Write(dr[0].ToString());
}
}

Best Luck
Happy Coding