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B. Estrade
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mysqldiff - compare MySQL database schemas


    mysqldiff [B<options>] B<database1> B<database2>

    mysqldiff --help


mysqldiff is a Perl script front-end to the CPAN module MySQL::Diff which compares the data structures (i.e. schema / table definitions) of two MySQL databases, and returns the differences as a sequence of MySQL commands suitable for piping into mysql which will transform the structure of the first database to be identical to that of the second (c.f. diff and patch).

Database structures can be compared whether they are files containing table definitions or existing databases, local or remote.

N.B. The program makes no attempt to compare any of the data which may be stored in the databases. It is purely for comparing the table definitions. I have no plans to implement data comparison; it is a complex problem and I have no need of such functionality anyway. However there is another program coldiff which does this, and is based on an older program called datadiff which seems to have vanished off the 'net.

For PostgreSQL there are similar tools such as pgdiff and apgdiff.


  # compare table definitions in two files
  mysqldiff db1.mysql db2.mysql

  # compare table definitions in a file 'db1.mysql' with a database 'db2'
  mysqldiff db1.mysql db2

  # interactively upgrade schema of database 'db1' to be like the
  # schema described in the file 'db2.mysql'
  mysqldiff -A db1 db2.mysql

  # compare table definitions in two databases on a remote machine
  mysqldiff --host=remote.host.com --user=myaccount db1 db2

  # compare table definitions in a local database 'foo' with a
  # database 'bar' on a remote machine, when a file foo already
  # exists in the current directory
  mysqldiff --host2=remote.host.com --password=secret db:foo bar


-?, --help

show usage

-A, --apply

interactively patch database1 to match database2

-B, --batch-apply

non-interactively patch database1 to match database2

-d, --debug[=N]

enable debugging [level N, default 1]

-l, --list-tables

output the list off all used tables

-o, --only-both

only output changes for tables in both databases

-k, --keep-old-tables

don't output DROP TABLE commands

-c, --keep-old-columns

don't output DROP COLUMN commands

-n, --no-old-defs

suppress comments describing old definitions

-t, --table-re=REGEXP

restrict comparisons to tables matching REGEXP

-i, --tolerant

ignore DEFAULT, AUTO_INCREMENT, COLLATE, and formatting changes

-S, --single-transaction

perform DB dump in transaction For more info see: http://dev.mysql.com/doc/refman/en/mysqldump.html#option_mysqldump_single-transaction

-h, --host=[hostname]

connect to host

-P, --port=[port]

use this port for connection

-u, --user=[user]

user for login if not current user

-p, --password[=password]

password to use when connecting to server

-s, --socket=...

socket to use when connecting to server

For <databaseN> only, where N == 1 or 2


connect to host


use this port for connection


user for login if not current user


password to use when connecting to server


socket to use when connecting to server


For both of the database structures being compared, the following happens:

  • If the argument is a valid filename, the file is used to create a temporary database which mysqldump -d is run on to obtain the table definitions in canonicalised form. The temporary database is then dropped. (The temporary database is named test_mysqldiff_temp_something because default MySQL permissions allow anyone to create databases beginning with the prefix test_.)

  • If the argument is a database, mysqldump -d is run directly on it.

  • Where authentication is required, the hostname, username, and password given by the corresponding options are used (type mysqldiff --help for more information).

  • Each set of table definitions is now parsed into tables, and fields and index keys within those tables; these are compared, and the differences outputted in the form of MySQL statements.


See http://adamspiers.org/computing/mysqldiff/.


Copyright (c) 2000-2016 Adam Spiers. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.


MySQL::Diff, MySQL::Diff::Database, MySQL::Diff::Table, MySQL::Diff::Utils, mysql, mysqldump, mysqlshow


Adam Spiers <mysqldiff@adamspiers.org>