MySQL Update multiple rows on a single column based on values from that same column

Question

I have a table that looks like the following:

ID     Key     Value     Order
1      gender  m         0
2      gender  f         0

34     age     10        0
35     age     80        0

To update these rows I have to use the following:

UPDATE `DemoGroup` SET `value` = 'male' WHERE `value` = 'm'
UPDATE `DemoGroup` SET `value` = 'female' WHERE `value` = 'f'
UPDATE `DemoGroup` SET `value` = '10-19' WHERE `value` = '10'
UPDATE `DemoGroup` SET `value` = '80-89' WHERE `value` = '80'

Is there a way to consolidate this into one update statement, without using the ID (which is not guaranteed to be the same), such as (even though this won't work)...

UPDATE `DemoGroup` 
SET `value`= CASE `value`
    WHEN 'm' THEN 'male',
    WHEN 'f' THEN 'female' END 
WHERE `value` = 'm' OR `value` = 'f'

Even more of a bonus (but not nessesary) is if I could figure out how to set the Order field as well for each row...

Answer 1

You should probably update the values based not only on the value of value but on the value of key , otherwise you could update 'm' to 'male' when key is 'shirt-size'.

UPDATE `DemoGroup` 
SET `value` = CASE 
    WHEN (`key`, `value`) = ('gender', 'm') THEN 'male'
    WHEN (`key`, `value`) = ('gender', 'f') THEN 'female'
    WHEN (`key`, `value`) = ('age', '10')   THEN '10-19'
    WHEN (`key`, `value`) = ('age', '80')   THEN '80-89'
    ELSE `value` -- no-op for other values
  END 
WHERE `key` IN ('gender','age');

Answer 2

MySQL does have a case function. Try:

UPDATE DemoGroup SET `value` = 
CASE `value` WHEN 'm' THEN 'male'
WHEN 'f' THEN 'female'
WHEN '10' THEN '10-19'
WHEN '80' THEN '80-89' END;