mySQL select differences between two tables in different databases

Question

I have two databases: old and new.
Both have a comments table. There are 100 comments in the old table that are not in the new. Comments have been added to the new table and there is a conflict in IDs so querying by ID will not be an option. I need so isolate the 100 comments that that they can be exported and inserted into the new database.

I know there are 100 because I have tried using some mysql data compare tools. Unfortunately all of those tools just want to update the comments in the new table with the old content.

Is there a query I can run to get the 100 comments?

The `CREATE TABLE` statement for the COMMENTS table would help... — OMG Ponies, May 31 '11 at 00:01

score 18 · Accepted Answer · edited May 23 '18 at 06:05

18

Assuming the tables aren't very large you can run something like this:

SELECT *
FROM OldDatabase.CommentTable
WHERE COMMENT NOT IN
    (SELECT COMMENT
     FROM NewDatabase.CommentTable)

edited May 23 '18 at 06:05

Pablo Bianchi

1,824
1
26
30

answered May 31 '11 at 00:04

Dave Maple

8,102
4
45
64

mySQL select differences between two tables in different databases

1 Answers1