如何根据同一表中的另一列数据填充一列？

Question

I have two sets of data I joined into a single table. One was USA addresses and the other was Canadian addresses. I need the option to be able to sort by Country. So I inserted a blank country column into my table and my table now looks like this:

 state | country | zip
-----------------------
       |         | 
       |         |

I have the state and zip data but my country column is empty. Since US zip code format is 5 digits (ex. 12345) and CAN zip are formatted like (ex. G5Y 5S7) is it possible with mysql to populate the country data with some sort of...

UPDATE table 
SET country = US 
WHERE zip (LIKE or =) (US zip format);

And then go back and use some sort of WHERE zip LIKE NULL to populate the rest of country data with CAN?

Thanks

Answer 1

You could check the length of the value in the zip column.

UPDATE table 
   set country = 'US'
 where char_length(zip) = 5;

then:

UPDATE table 
   set country = 'CAN'
 where country is null

-- or, in one go --

UPDATE table t
   set country = 
  (case when char_length(t.zip) = 5
   then 'US'
  else 'CAN'
  end);