comparing rows to find updated cells

[mameha]

I have a table of data that should be updated every 3 hours by a new set of data. 

 

I put the new data into a new table, and now I want to compare the two tables to find what data has been updated.

 

For example:

 

OLD TABLE

id | height | width

123 | 55 | 80

 

NEW TABLE

id | height | width

123 | 65 | 80

 

As you can see, height has been updated to 65. 

 

Is there some query that can (1) find all rows that have been updated and (2) tell me which column was updated?

[luca200]

SELECT n.id, if(n.height != o.height, n.height, null) as height, if(n.width != o.width, n.width, null) as width
from newtable n join oldtable o on n.id = o.id
where (o.height != n.height or o.width != n.width)

 

Not tested, just try it 

You should get a row for every id that has at least one column updated, and a NULL value for not updated values

 

 

[fenway]

Actually, you should jeft join and use IFNULL to decide.