Tricky Update in the same table

I have a query that yield a result like this

col1ID      col2      Name1      col3ID        col4       Name2      

1             200          A             1               null         null

2             null          null           2              300         A

1             400          B              1              null          null

2             null          null           2              500         B

There is no unique ID for this table, say Extbl, colIDID and col3ID has the same value, either col2 or col3 has null value, also Name1 and Name2 has null value, how can I update Extbl to have result like this?

col1ID      col2      Name1      col3ID        col4       Name2      

1             200          A           1               200         A

2             300          A           2              300         A

1             400          B           1               400         B

2             500          B           2              500         B

Thank you

Kay_D