SQL Syntax Reference : DROP DATABASE
 
DROP DATABASE
The DROP DATABASE statement deletes a database. Only the Master user can issue this statement.
Syntax
DROP DATABASE [ IF EXISTS ] database-name [ DELETE FILES ]
 
database-name ::= user-defined-name
Remarks
As Master user, you must be logged on to a database to issue the statement. The DROP DATABASE statement can be used to drop any database, including the one to which you are currently logged on, provided the security setting permits deletion. See Secured Databases below.
DROP DATABASE cannot be used to delete system databases such as defaultdb and tempdb. The statement can be used to delete the last remaining user-defined database if you choose, security permitting.
The DROP DATABASE statement cannot be used in a stored procedure or in a user-defined function.
The expression IF EXISTS causes the statement to return success instead of an error if a database does not exist. IF EXISTS does not suppress other errors.
Secured Databases
You cannot delete a database secured with the Database security model. You can delete a database secured with any of the following ways:
Classic security
Mixed security
Relational security (Master password) in combination with Classic or Mixed security
For more information, see PSQL Security in Advanced Operations Guide.
DELETE FILES
The DELETE FILES clause is for deleting data dictionary files (DDFs). Data files are not deleted.
If DELETE FILES is omitted, the DDFs remain on physical storage, but the database name is deleted from dbnames.cfg. Once the name is removed from dbnames.cfg, the database no longer exists to the database engine. Retaining the DDFs allows you to recreate the database should you so choose.
Note that the DDFs must not be in use to delete them. If you have PSQL Control Center open, for example, a “file is locked” error returns if you use the DELETE FILES clause. While PCC is open, the DDFs are considered to be in use, which prevents their deletion.
Examples
The following example deletes a database named inventorydb from dbnames.cfg, but it retains the database DDFs (and data files) in physical storage.
DROP DATABASE inventorydb
============ 
The following example deletes a database named HRUSBenefits and its DDFs. Data files are retained for HRUSBenefits.
DROP DATABASE HRUSBenefits DELETE FILES
See Also
CREATE DATABASE