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MySQL 5.5 Reference Manual
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2.12 Downgrading MySQL

This section describes the steps to downgrade a MySQL installation.

Downgrading is a less common operation than upgrade. Downgrading is typically performed because of a compatibility or performance issue that occurs on a production system, and was not uncovered during initial upgrade verification on the test systems. As with the upgrade procedure verification on the test systems. As with the upgrade procedure Section 2.11, “Upgrading MySQL”), perform and verify the downgrade procedure on some test systems first, before using it on a production system.

Note

In the following discussion, MySQL commands that must be run using a MySQL account with administrative privileges include -u root on the command line to specify the MySQL root user. Commands that require a password for root also include a -p option. Because -p is followed by no option value, such commands prompt for the password. Type the password when prompted and press Enter.

SQL statements can be executed using the mysql command-line client (connect as root to ensure that you have the necessary privileges).


User Comments
User comments in this section are, as the name implies, provided by MySQL users. The MySQL documentation team is not responsible for, nor do they endorse, any of the information provided here.
  Posted by Mathias Karlsson on May 31, 2011
For downgrades from 5.5 to 5.1, the mysql.proc table can be fixed by executing
ALTER TABLE `mysql`.`proc` MODIFY COLUMN `comment` CHAR(64) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL DEFAULT '';