PostgreSQL - DROP Database - Adglob Infosystem Pvt Ltd

In this chapter, we will discuss how to delete the database in PostgreSQL. There are two options to delete a database −

Using DROP DATABASE, an SQL command.
Using dropdb a command-line executable.

Be careful before using this operation because deleting an existing database would result in loss of complete information stored in the database.

Using DROP DATABASE

This command drops a database. It removes the catalog entries for the database and deletes the directory containing the data. It can only be executed by the database owner. This command cannot be executed while you or anyone else is connected to the target database (connect to postgres or any other database to issue this command).

Syntax

The syntax for DROP DATABASE is given below −

DROP DATABASE [ IF EXISTS ] name

Parameters

The table lists the parameters with their descriptions.

S. No.	Parameter & Description
1	IF EXISTSDo not throw an error if the database does not exist. A notice is issued in this case.
2	nameThe name of the database to remove.

We cannot drop a database that has any open connections, including our own connection from psql or pgAdmin III. We must switch to another database or template1 if we want to delete the database we are currently connected to. Thus, it might be more convenient to use the program dropdb instead, which is a wrapper around this command.

Example

The following is a simple example, which will delete testdb from your PostgreSQL schema −

postgres=# DROP DATABASE testdb;
postgres-#

Using dropdb Command

PostgresSQL command line executable dropdb is a command-line wrapper around the SQL command DROP DATABASE. There is no effective difference between dropping databases via this utility and via other methods for accessing the server. dropdb destroys an existing PostgreSQL database. The user, who executes this command must be a database super user or the owner of the database.

Syntax

The syntax for dropdb is as shown below −

dropdb  [option...] dbname

Parameters

The following table lists the parameters with their descriptions

S. No.	Parameter & Description
1	dbnameThe name of a database to be deleted.
2	optioncommand-line arguments, which dropdb accepts.

Options

The following table lists the command-line arguments dropdb accepts −

S. No.	Option & Description
1	-eShows the commands being sent to the server.
2	-iIssues a verification prompt before doing anything destructive.
3	-VPrint the dropdb version and exit.
4	–if-existsDo not throw an error if the database does not exist. A notice is issued in this case.
5	–helpShow help about dropdb command-line arguments, and exit.
6	-h hostSpecifies the host name of the machine on which the server is running.
7	-p portSpecifies the TCP port or the local UNIX domain socket file extension on which the server is listening for connections.
8	-U usernameUser name to connect as.
9	-wNever issue a password prompt.
10	-WForce dropdb to prompt for a password before connecting to a database.
11	–maintenance-db=dbnameSpecifies the name of the database to connect to in order to drop the target database.

Example

The following example demonstrates deleting a database from OS command prompt −

dropdb -h localhost -p 5432 -U postgress testdb
Password for user postgress: ****

The above command drops the database testdb. Here, I have used the postgres (found under the pg_roles of template1) username to drop the database.