在PG 12或以下版本，刪除資料庫時如存在連線則無法刪除，PG 13提供了force選項，可終止相關連線直接刪除資料庫。

**PG 12**
建立資料庫並連線
```
[pg12@localhost ~]$ createdb dropdb
[pg12@localhost ~]$ 
[pg12@localhost ~]$ psql -d dropdb
Expanded display is used automatically.
psql (12.1)
Type "help" for help.

[local:/run/pg12]:5120 pg12@dropdb=#

```
刪除資料庫，一直在等待，超時後提示
```
[pg12@localhost ~]$ psql
Expanded display is used automatically.
psql (12.1)
Type "help" for help.

[local:/run/pg12]:5120 pg12@testdb=# drop database dropdb;
ERROR:  database "dropdb" is being accessed by other users
DETAIL:  There is 1 other session using the database.

```

**PG 13**
建立資料庫並連線
```
[pg13@localhost ~]$ createdb dropdb
[pg13@localhost ~]$ psql -d dropdb
Expanded display is used automatically.
psql (13devel)
Type "help" for help.

[local:/run/pg13]:5130 pg13@dropdb=#

```
刪除資料庫，提示無法刪除資料庫
```
[pg13@localhost ~]$ psql
Expanded display is used automatically.
psql (13devel)
Type "help" for help.

[local:/run/pg13]:5130 pg13@masterdb=# drop database dropdb;
ERROR:  database "dropdb" is being accessed by other users
DETAIL:  There is 1 other session using the database.
[local:/run/pg13]:5130 pg13@masterdb=#

```
使用force選項刪除
```
[local:/run/pg13]:5130 pg13@masterdb=# drop database dropdb with(force);
DROP DATABASE
[local:/run/pg13]:5130 pg13@masterdb=#

```
回到連線dropdb資料庫的session，該session已被drop
```
[local:/run/pg13]:5130 pg13@dropdb=# select 1;
FATAL:  terminating connection due to administrator command
server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
: @!>?

```

**參考資料**
[Waiting for PostgreSQL 13 – Introduce the ‘force’ option for the Drop Database command.](https://www.depesz.com/2019/11/16/waiting-for-postgresql-13-introduce-the-force-option-for-the-drop-database-command/)

PostgreSQL DBA(138) - PG 13（Drop database force）

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