I could database you could database he could database we could database you could database they could database
V-ing form
I could be databasing you could be databasing he could be databasing we could be databasing you could be databasing they could be databasing
Perfect
I could have databased you could have databased he could have databased we could have databased you could have databased they could have databased
V-ing perfect
I could have been databasing you could have been databasing he could have been databasing we could have been databasing you could have been databasing they could have been databasing
Negation
Simple form
I couldn't database you couldn't database he couldn't database we couldn't database you couldn't database they couldn't database
V-ing form
I couldn't be databasing you couldn't be databasing he couldn't be databasing we couldn't be databasing you couldn't be databasing they couldn't be databasing
Perfect
I couldn't have databased you couldn't have databased he couldn't have databased we couldn't have databased you couldn't have databased they couldn't have databased
V-ing perfect
I couldn't have been databasing you couldn't have been databasing he couldn't have been databasing we couldn't have been databasing you couldn't have been databasing they couldn't have been databasing
Interrogative form
Simple form
could I database? could you database? could he database? could we database? could you database? could they database?
V-ing form
could I be databasing? could you be databasing? could he be databasing? could we be databasing? could you be databasing? could they be databasing?
Perfect
could I have databased? could you have databased? could he have databased? could we have databased? could you have databased? could they have databased?
V-ing perfect
could I have been databasing? could you have been databasing? could he have been databasing? could we have been databasing? could you have been databasing? could they have been databasing?
Interro-negative form
Simple form
couldn't I database? couldn't you database? couldn't he database? couldn't we database? couldn't you database? couldn't they database?
V-ing form
couldn't I be databasing? couldn't you be databasing? couldn't he be databasing? couldn't we be databasing? couldn't you be databasing? couldn't they be databasing?
Perfect
couldn't I have databased? couldn't you have databased? couldn't he have databased? couldn't we have databased? couldn't you have databased? couldn't they have databased?
V-ing perfect
couldn't I have been databasing? couldn't you have been databasing? couldn't he have been databasing? couldn't we have been databasing? couldn't you have been databasing? couldn't they have been databasing?