function use in sql -- md5

Hi friends! I have a mysql column full of plain text passwords that I'd like to hash via MD5. I can think of looping through and updating through php but am hoping to learn a little trick to speed up similar activities in the future. All thoughts and tips welcome for updating, ideally at the shell level, which is one of my current weaknesses. This will not work but is the idea (after setting (32) : update mycolumn set mycolumn = md5(mycolumn); What would be proper syntax to complete this goal? How would YOU approach this? TIA, Philip -- be outside the box.