For this you need to follow this steps..
1) First of all count a total record in your table using this query..
SELECT COUNT(*) FROM "YOUR TABLE NAME"
this query resulted in total number of record in your table..
store this result in one int Row.
2) Now calculate half row like this int Counter = row/2;
3) after getting total no of record now fire this select query..
SELECT * FROM "YOUR TABLE" WHERE ID <= @COUNTER ORDER BY ID
4) Here @Counter is a parameter you need to pass.
5) Now fill your DataTable or DataSet with the result of 2 steps query.
6) assining a datasource to your gridview 1
7) Now Fire Second Query
SELECT * FROM "YOUR TABLE" WHERE ID > @COUNTER ORDER BY ID
8) Now fill your second datatable or dataset and assign it to as datasource to your gridview 2
by this you can fill your table's data halfly to one grid and halfly to secod grid as per your requirement.
like this you can write your own query with your divided criteria on which base you want to divide data in tow grid.
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