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 Data Definition (DDL) StatementsSHADOW 

Optional Parameters for CREATE DATABASE

USER and PASSWORD

The username and the password of an existing user in the security database ({secdb} or whatever is configured in the SecurityDatabase configuration).You do not have to specify the username and password if the ISC_USER and ISC_PASSWORD environment variables are set.The user specified in the process of creating the database will be its owner.This will be important when considering database and object privileges.

ROLE

The name of the role (usually RDB$ADMIN), which will be taken into account when creating the database.The role must be assigned to the user in the applicable security database.

PAGE_SIZE

The desired database page size.This size will be set for the primary file and all secondary files of the database.If you specify the database page size less than 4,096, it will be automatically rounded up to 4,096.Other values not equal to either 4,096, 8,192, 16,384 or 32,768 will be changed to the closest smaller supported value.If the database page size is not specified, the default value of 8,192 is used.

Note
Bigger Isn’t Always Better.

Larger page sizes can fit more records on a single page, have wider indexes, and more indexes, but they will also waste more space for blobs (compare the wasted space of a 3KB blob on page size 4096 with one on 32768: +/- 1KB vs +/- 29KB), and increase memory consumption of the page cache.
LENGTH

The maximum size of the primary or secondary database file, in pages.When a database is created, its primary and secondary files will occupy the minimum number of pages necessary to store the system data, regardless of the value specified in the LENGTH clause.The LENGTH value does not affect the size of the only (or last, in a multi-file database) file.The file will keep increasing its size automatically when necessary.

SET NAMES

The character set of the connection available after the database is successfully created.The character set NONE is used by default.Notice that the character set should be enclosed in a pair of apostrophes (single quotes).

DEFAULT CHARACTER SET

The default character set for creating data structures of string data types.Character sets are used for CHAR, VARCHAR and BLOB SUB_TYPE TEXT data types.The character set NONE is used by default.It is also possible to specify the default COLLATION for the default character set, making that collation the default for the default character set.The default will be used for the entire database except where an alternative character set, with or without a specified collation, is used explicitly for a field, domain, variable, cast expression, etc.

STARTING AT

The database page number at which the next secondary database file should start.When the previous file is fully filled with data according to the specified page number, the system will start adding new data to the next database file.

DIFFERENCE FILE

The path and name for the file delta that stores any mutations to the database file after it has been switched to the “copy-safe” mode by the ALTER DATABASE BEGIN BACKUP statement.For the detailed description of this clause, see [fblangref50-ddl-db-alter].

Specifying the Database Dialect

Databases are created in Dialect 3 by default.For the database to be created in Dialect 1, you will need to execute the statement SET SQL DIALECT 1 from script or the client application, e.g. in isql, before the CREATE DATABASE statement.

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Who Can Create a Database

The CREATE DATABASE statement can be executed by:

Examples Using CREATE DATABASE

  1. Creating a database in Windows, located on disk D with a page size of 4,096.The owner of the database will be the user wizard.The database will be in Dialect 1, and will use WIN1251 as its default character set.

    SET SQL DIALECT 1;
CREATE DATABASE 'D:\test.fdb'
USER 'wizard' PASSWORD 'player'
PAGE_SIZE = 4096 DEFAULT CHARACTER SET WIN1251;

  2. Creating a database in the Linux operating system with a page size of 8,192 (default).The owner of the database will be the user wizard.The database will be in Dialect 3 and will use UTF8 as its default character set, with UNICODE_CI_AI as the default collation.

    CREATE DATABASE '/home/firebird/test.fdb'
USER 'wizard' PASSWORD 'player'
DEFAULT CHARACTER SET UTF8 COLLATION UNICODE_CI_AI;

  3. Creating a database on the remote server “baseserver” with the path specified in the alias “test” that has been defined previously in the file databases.conf.The TCP/IP protocol is used.The owner of the database will be the user wizard.The database will be in Dialect 3 and will use UTF8 as its default character set.

    CREATE DATABASE 'baseserver:test'
USER 'wizard' PASSWORD 'player'
DEFAULT CHARACTER SET UTF8;

  4. Creating a database in Dialect 3 with UTF8 as its default character set.The primary file will contain up to 10,000 pages with a page size of 8,192.As soon as the primary file has reached the maximum number of pages, Firebird will start allocating pages to the secondary file test.fdb2.If that file is filled up to its maximum as well, test.fdb3 becomes the recipient of all new page allocations.As the last file, it has no page limit imposed on it by Firebird.New allocations will continue for as long as the file system allows it or until the storage device runs out of free space.If a LENGTH parameter were supplied for this last file, it would be ignored.

    SET SQL DIALECT 3;
CREATE DATABASE 'baseserver:D:\test.fdb'
USER 'wizard' PASSWORD 'player'
PAGE_SIZE = 8192
DEFAULT CHARACTER SET UTF8
FILE 'D:\test.fdb2'
STARTING AT PAGE 10001
FILE 'D:\test.fdb3'
STARTING AT PAGE 20001;

  5. Creating a database in Dialect 3 with UTF8 as its default character set.The primary file will contain up to 10,000 pages with a page size of 8,192.As far as file size and the use of secondary files are concerned, this database will behave exactly like the one in the previous example.

    SET SQL DIALECT 3;
CREATE DATABASE 'baseserver:D:\test.fdb'
USER 'wizard' PASSWORD 'player'
PAGE_SIZE = 8192
LENGTH 10000 PAGES
DEFAULT CHARACTER SET UTF8
FILE 'D:\test.fdb2'
FILE 'D:\test.fdb3'
STARTING AT PAGE 20001;
See also

[fblangref50-ddl-db-alter], [fblangref50-ddl-db-drop]

ALTER DATABASE

Alters the file organisation of a database, toggles its “copy-safe” state, manages encryption, and other database-wide configuration

Available in

DSQL, ESQL — limited feature set

Syntax
ALTER {DATABASE | SCHEMA} <alter_db_option> [<alter_db_option> ...]

<alter_db_option> :==
    <add_sec_clause>
  | {ADD DIFFERENCE FILE 'diff_file' | DROP DIFFERENCE FILE}
  | {BEGIN | END} BACKUP
  | SET DEFAULT CHARACTER SET charset
  | {ENCRYPT WITH plugin_name [KEY key_name] | DECRYPT}
  | SET LINGER TO linger_duration
  | DROP LINGER
  | SET DEFAULT SQL SECURITY {INVOKER | DEFINER}
  | {ENABLE | DISABLE} PUBLICATION
  | INCLUDE <pub_table_filter> TO PUBLICATION
  | EXCLUDE <pub_table_filter> FROM PUBLICATION

<add_sec_clause> ::= ADD <sec_file> [<sec_file> ...]

<sec_file> ::=
  FILE 'filepath'
  [STARTING [AT [PAGE]] pagenum]
  [LENGTH [=] num [PAGE[S]]

<pub_table_filter> ::=
    ALL
  | TABLE table_name [, table_name ...]
Note

Multiple files can be added in one ADD clause:

ALTER DATABASE
  ADD FILE x LENGTH 8000
    FILE y LENGTH 8000
    FILE z

Multiple occurrences of add_sec_clause (ADD FILE clauses) are allowed;an ADD FILE clause that adds multiple files (as in the example above) can be mixed with others that add only one file.
Table 1. ALTER DATABASE Statement Parameters
Parameter Description

add_sec_clause

Adding a secondary database file

sec_file

File specification for secondary file

filepath

Full path and file name of the delta file or secondary database file

pagenum

Page number from which the secondary database file is to start

num

Maximum size of the secondary file in pages

diff_file

File path and name of the .delta file (difference file)

charset

New default character set of the database

linger_duration

Duration of linger delay in seconds;must be greater than or equal to 0 (zero)

plugin_name

The name of the encryption plugin

key_name

The name of the encryption key

pub_table_filter

Filter of tables to include to or exclude from publication

table_name

Name (identifier) of a table

The ALTER DATABASE statement can:

  • add secondary files to a database

  • switch a single-file database into and out of the “copy-safe” mode (DSQL only)

  • set or unset the path and name of the delta file for physical backups (DSQL only)

Note

SCHEMA is currently a synonym for DATABASE;this may change in a future version, so we recommend to always use DATABASE

Who Can Alter the Database

The ALTER DATABASE statement can be executed by:

Parameters for ALTER DATABASE

ADD (FILE)

Adds secondary files to the database.It is necessary to specify the full path to the file and the name of the secondary file.The description for the secondary file is similar to the one given for the CREATE DATABASE statement.

ADD DIFFERENCE FILE

Specifies the path and name of the difference file (or, delta file) that stores any mutations to the database whenever it is switched to the “copy-safe” mode.This clause does not add a file, but it configures name and path of the delta file when the database is in “copy-safe” mode.To change the existing setting, you should delete the previously specified description of the delta file using the DROP DIFFERENCE FILE clause before specifying the new description of the delta file.If the path and name of the delta file are not configured, the file will have the same path and name as the database, but with the .delta file extension.

Caution

If only a filename is specified, the delta file will be created in the current directory of the server.On Windows, this will be the system directory — a very unwise location to store volatile user files and contrary to Windows file system rules.
DROP DIFFERENCE FILE

Deletes the description (path and name) of the difference file specified previously in the ADD DIFFERENCE FILE clause.This does not delete a file, but DROP DIFFERENCE FILE clears (resets) the path and name of the delta file from the database header.Next time the database is switched to the “copy-safe” mode, the default values will be used (i.e. the same path and name as those of the database, but with the .delta extension).

BEGIN BACKUP

Switches the database to the “copy-safe” mode.ALTER DATABASE with this clause freezes the main database file, making it possible to back it up safely using file system tools, even if users are connected and performing operations with data.Until the backup state of the database is reverted to NORMAL, all changes made to the database will be written to the delta (difference) file.

Important

Despite its name, the ALTER DATABASE BEGIN BACKUP statement does not start a backup process, but only freezes the database, to create the conditions for doing a task that requires the database file to be read-only temporarily.
END BACKUP

Switches the database from the “copy-safe” mode to the normal mode.A statement with this clause merges the difference file with the main database file and restores the normal operation of the database.Once the END BACKUP process starts, the conditions no longer exist for creating safe backups by means of file system tools.

Warning

Use of BEGIN BACKUP and END BACKUP and copying the database files with filesystem tools, is not safe with multi-file databases!Use this method only on single-file databases.

Making a safe backup with the gbak utility remains possible at all times, although it is not recommended running gbak while the database is in LOCKED or MERGE state.
SET DEFAULT CHARACTER SET

Changes the default character set of the database.This change does not affect existing data or columns.The new default character set will only be used in subsequent DDL commands.To modify the default collation, use ALTER CHARACTER SET on the default character set of the database.

ENCRYPT WITH

See Encrypting a Database in the Security chapter.

DECRYPT

See Decrypting a Database in the Security chapter.

SET LINGER TO

Sets the linger-delay.The linger-delay applies only to Firebird SuperServer, and is the number of seconds the server keeps a database file (and its caches) open after the last connection to that database was closed.This can help to improve performance at low cost, when the database is opened and closed frequently, by keeping resources “warm” for the next connection.

Note

This mode can be useful for web applications — without a connection pool — where connections to the database usually “live” for a very short time.
Warning

The SET LINGER TO and DROP LINGER clauses can be combined in a single statement, but the last clause “wins”.For example, ALTER DATABASE SET LINGER TO 5 DROP LINGER will set the linger-delay to 0 (no linger), while ALTER DATABASE DROP LINGER SET LINGER to 5 will set the linger-delay to 5 seconds.
DROP LINGER

Drops the linger-delay (sets it to zero).Using DROP LINGER is equivalent to using SET LINGER TO 0.

Note

Dropping LINGER is not an ideal solution for the occasional need to turn it off for once-only operations where the server needs a forced shutdown.The gfix utility now has the -NoLinger switch, which will close the specified database immediately after the last attachment is gone, regardless of the LINGER setting in the database.The LINGER setting is retained and works normally the next time.

The same one-off override is also available through the Services API, using the tag isc_spb_prp_nolinger, e.g. (in one line):

fbsvcmgr host:service_mgr user sysdba password xxx
       action_properties dbname employee prp_nolinger
Warning

The DROP LINGER and SET LINGER TO clauses can be combined in a single statement, but the last clause “wins”.
SET DEFAULT SQL SECURITY

Specifies the default SQL SECURITY option to apply at runtime for objects without the SQL Security property set.See also SQL Security in chapter Security.

ENABLE PUBLICATION

Enables publication of this database for replication.Replication begins (or continues) with the next transaction started after this transaction commits.

DISABLE PUBLICATION

Enables publication of this database for replication.Replication is disabled immediately after commit.

EXCLUDE …​ FROM PUBLICATION

Excludes tables from publication.If the INCLUDE ALL TO PUBLICATION clause is used, all tables created afterward will also be replicated, unless overridden explicitly in the CREATE TABLE statement.

INCLUDE …​ TO PUBLICATION

Includes tables to publication.If the INCLUDE ALL TO PUBLICATION clause is used, all tables created afterward will also be replicated, unless overridden explicitly in the CREATE TABLE statement.

Note
Replication

  • Other than the syntax, configuring Firebird for replication is not covered in this language reference.

  • All replication management commands are DDL statements and thus effectively executed at the transaction commit time.

Examples of ALTER DATABASE Usage

  1. Adding a secondary file to the database.As soon as 30000 pages are filled in the previous primary or secondary file, the Firebird engine will start adding data to the secondary file test4.fdb.

    ALTER DATABASE
  ADD FILE 'D:\test4.fdb'
    STARTING AT PAGE 30001;

  2. Specifying the path and name of the delta file:

    ALTER DATABASE
  ADD DIFFERENCE FILE 'D:\test.diff';

  3. Deleting the description of the delta file:

    ALTER DATABASE
  DROP DIFFERENCE FILE;

  4. Switching the database to the “copy-safe” mode:

    ALTER DATABASE
  BEGIN BACKUP;

  5. Switching the database back from the “copy-safe” mode to the normal operation mode:

    ALTER DATABASE
  END BACKUP;

  6. Changing the default character set for a database to WIN1251

    ALTER DATABASE
  SET DEFAULT CHARACTER SET WIN1252;

  7. Setting a linger-delay of 30 seconds

    ALTER DATABASE
  SET LINGER TO 30;

  8. Encrypting the database with a plugin called DbCrypt

    ALTER DATABASE
  ENCRYPT WITH DbCrypt;

  9. Decrypting the database

    ALTER DATABASE
  DECRYPT;
See also

[fblangref50-ddl-db-create], [fblangref50-ddl-db-drop]

DROP DATABASE

Drops (deletes) the database of the current connection

Available in

DSQL, ESQL

Syntax
DROP DATABASE

The DROP DATABASE statement deletes the current database.Before deleting a database, you have to connect to it.The statement deletes the primary file, all secondary files and all shadow files.

Note

Contrary to CREATE DATABASE and ALTER DATABASE, DROP SCHEMA is not a valid alias for DROP DATABASE.This is intentional.

Who Can Drop a Database

The DROP DATABASE statement can be executed by:

Example of DROP DATABASE

Deleting the current database
DROP DATABASE;
See also

[fblangref50-ddl-db-create], [fblangref50-ddl-db-alter]