MySQL 5.7 Release Notes
ALTER {DATABASE | SCHEMA} [db_name]
alter_option ...
ALTER {DATABASE | SCHEMA} db_name
UPGRADE DATA DIRECTORY NAME
alter_option: {
[DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name
}
ALTER DATABASE enables you to
change the overall characteristics of a database. These
characteristics are stored in the db.opt file
in the database directory. This statement requires the
ALTER privilege on the database.
ALTER
SCHEMA is a synonym for ALTER
DATABASE.
The database name can be omitted from the first syntax, in which case the statement applies to the default database. An error occurs if there is no default database.
Character Set and Collation Options
The CHARACTER SET clause changes the default
database character set. The COLLATE clause
changes the default database collation. For information about
character set and collation names, see Chapter 10, Character Sets, Collations, Unicode.
To see the available character sets and collations, use the
SHOW CHARACTER SET and
SHOW COLLATION statements,
respectively. See Section 13.7.5.3, “SHOW CHARACTER SET Statement”, and
Section 13.7.5.4, “SHOW COLLATION Statement”.
A stored routine that uses the database defaults when the routine is created includes those defaults as part of its definition. (In a stored routine, variables with character data types use the database defaults if the character set or collation are not specified explicitly. See Section 13.1.16, “CREATE PROCEDURE and CREATE FUNCTION Statements”.) If you change the default character set or collation for a database, any stored routines that are to use the new defaults must be dropped and recreated.
Upgrading from Versions Older than MySQL 5.1
The syntax that includes the UPGRADE DATA DIRECTORY
NAME clause updates the name of the directory associated
with the database to use the encoding implemented in MySQL 5.1 for
mapping database names to database directory names (see
Section 9.2.4, “Mapping of Identifiers to File Names”). This clause is for use
under these conditions:
It is intended when upgrading MySQL to 5.1 or later from older versions.
It is intended to update a database directory name to the current encoding format if the name contains special characters that need encoding.
The statement is used by mysqlcheck (as invoked by mysql_upgrade).
For example, if a database in MySQL 5.0 has the name
a-b-c, the name contains instances of the
- (dash) character. In MySQL 5.0, the database
directory is also named a-b-c, which is not
necessarily safe for all file systems. In MySQL 5.1 and later, the
same database name is encoded as a@002db@002dc
to produce a file system-neutral directory name.
When a MySQL installation is upgraded to MySQL 5.1 or later from
an older version,the server displays a name such as
a-b-c (which is in the old format) as
#mysql50#a-b-c, and you must refer to the name
using the #mysql50# prefix. Use
UPGRADE DATA DIRECTORY NAME in this case to
explicitly tell the server to re-encode the database directory
name to the current encoding format:
ALTER DATABASE `#mysql50#a-b-c` UPGRADE DATA DIRECTORY NAME;
After executing this statement, you can refer to the database as
a-b-c without the special
#mysql50# prefix.
Note
The UPGRADE DATA DIRECTORY NAME clause is
deprecated in MySQL 5.7 and removed in MySQL
8.0. If it is necessary to convert MySQL 5.0 database
or table names, a workaround is to upgrade a MySQL 5.0
installation to MySQL 5.1 before upgrading to MySQL
8.0.