使用更新将行复制到另一个表中

Question

Ok, the title may be difficult to understand, but this is what I want to do.

I have a Table 'A' with a few columns. I have a Table 'B' with the exact same columns.

During my program flow, I insert a few rows from 'A' into 'B' (sort of a temp cache). Column data in 'A' may change, but when someone clicks the 'restore' button, I wanna copy those rows from 'B' back into 'A' and overwrite those rows with the same id as the ones i want to copy from 'B'.

Eg

Table A:

1  :      Hi |
2  :      Friends |
3  :      What's up

During the flow i backup id 1 and 2

Table B:

1  :      Hi |
2  :      Friends

Now I do some stuff and table A changes a bit

Table A (changed):

1 :       Hi diddely doo |
2 :       Amigo's |
3 :       What's up 

Now I realise my changes are wrong, and I want to put the records with id 1 and 2 back in their original state, from table 'B'.

Is there a 'simple' sql to do that, without fetching those id's 1 by 1 and update it 1 by 1?

Thanks in advance!

Answer 1

You can use JOIN in UPDATE statements :

UPDATE ta SET ta.text = tb.text
INNER JOIN tb ON ta.id = tb.id

Or with implicit join:

UPDATE ta, tb SET ta.text = tb.text
WHERE ta.id = tb.id

You can delete and reinsert, that way you don't have to specify columns if both tables have the same table scheme:

DELETE FROM ta WHERE id IN (SELECT id FROM tb)

INSERT INTO ta
SELECT * FROM tb