how can make datagridcomboboxcolumn with sql data

Question

Hi friends, I have a four column in datagridview. first three are textboxcell and final one is comboboxcolumn. when i insert data to sql server i can select any one of value from combobox. but updating process i just retrieve data from sql database will only give selected value. how can set all available value for combobox column and returned selected value in the current index. please help me.