sql - replace data in column B with data from column A timestamp Null -

i have sybase database trying replace data 1 column when columns data type timestamp , column trying move data has nulls trying replace.

date                             redemption_date 04-03-2010 09:21:14.462          04-03-2010 09:21:14.462 04-03-2010 09:21:14.462          (null) 04-03-2010 09:21:14.462          (null) 04-03-2010 09:21:14.462          04-03-2010 09:21:14.462 

the result

date                             redemption_date 04-03-2010 09:21:14.462          04-03-2010 09:21:14.462 04-03-2010 09:21:14.462          04-03-2010 09:21:14.462 04-03-2010 09:21:14.462          04-03-2010 09:21:14.462 04-03-2010 09:21:14.462          04-03-2010 09:21:14.462    

i have tried -

update accounts_receivable set redemption_date = date update table_name set column_b = column_a 

thanks jeff

you on right track. paul kienitz said in comment, need add where clause filter records want update. try like:

update accounts_receivable set redemption_date = date redemption_date null; 

this copy data date column redemption_date column wherever redemption_date field (null)