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

问题

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...

回答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');

回答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;

来源：https://stackoverflow.com/questions/7261656/mysql-update-multiple-rows-on-a-single-column-based-on-values-from-that-same-col

标签

mysql

entity-attribute-value