I need a suggestion about DataGridView and DataTable

I need a suggestion that might give me a proper idea. I have two tables in MS SQL 2008 Express. When my project open a WinForm that retrieve the data from DB as binding that to a DGW. So far so good but after an exact choosing to make an action that  inserts data one of tables and the other action inserts data to the other table so I need to show both actions' data in a DGW together. Each time after an action to either of those tables I must show that in the DGW with the data which retrieved when WinForm calls and appears on the screen.
What way might be good to handle this approach? Do I insert data either of the actions into SQL and show the data in DGW or store the data until the WinForm close then insert the data into SQL? I need opinions.