mysql：从备份中恢复列的值

Question

I'm having trouble. Instead of launchin script

UPDATE table_name SET field=value WHERE id=12345

I launched

UPDATE table_name SET field=value

Database is backuped every day (with mysqldump). What is the simpliest way to restore the value of that column using the backup. obviously I cannot apply that backup dirrectly as database is continiously changed.

Thank you in advance!!

Answer 1

I would create a new table 'table_name2' identical to your 'table_name' but containing the data of your backup.

Then use this query:

UPDATE table_name SET
table_name.field = (SELECT table_name2.field 
                    FROM table_name2 
                    WHERE table_name.id = table_name2.id)

Answer 2

So you wiped out all values in the column and want to put all values back in the correct rows?

I would recommend unzipping the backup into a separate database and doing something like

    UPDATE live_db.table_name live 
INNER JOIN backup_db.table_name backup
        ON live.id = backup.id 
       SET live.field = backup.field

I would also recommend making a duplicate of your live site to try this on first ;)

Answer 3

I would restore the backup of the table in another table called table_name_bck, then run the following sql.

UPDATE table_name_bck tb, table_name t
SET t.field = tb.field
WHERE tb.id = t.id

Of course try this in a test environment before to prevent worsening your situation.

Source: http://www.electrictoolbox.com/article/mysql/cross-table-update/

Answer 4

您可以尝试将备份加载到另一个数据库中，然后进行类似的操作（假设 db1 是生产数据库，而 db2 是临时数据库）

update db1.table set db1.field = db2.field where db1.id = db2.id