> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/tutorial/tutorial-start/tutorial-accessdb.md).

# 1.4. Accessing a Database \#

Once you have created a database, you can access it by:

* Running the PostgreSQL interactive terminal program, called *psql*, which allows you to interactively enter, edit, and execute SQL commands.
* Using an existing graphical frontend tool like pgAdmin or an office suite with ODBC or JDBC support to create and manipulate a database. These possibilities are not covered in this tutorial.
* Writing a custom application, using one of the several available language bindings. These possibilities are discussed further in [Part IV](/client-interfaces.md).

You probably want to start up `psql` to try the examples in this tutorial. It can be activated for the `mydb` database by typing the command:

```

$ psql mydb
```

If you do not supply the database name then it will default to your user account name. You already discovered this scheme in the previous section using `createdb`.

In `psql`, you will be greeted with the following message:

```

psql (18.6)
Type "help" for help.

mydb=>
```

The last line could also be:

```

mydb=#
```

That would mean you are a database superuser, which is most likely the case if you installed the PostgreSQL instance yourself. Being a superuser means that you are not subject to access controls. For the purposes of this tutorial that is not important.

If you encounter problems starting `psql` then go back to the previous section. The diagnostics of `createdb` and `psql` are similar, and if the former worked the latter should work as well.

The last line printed out by `psql` is the prompt, and it indicates that `psql` is listening to you and that you can type SQL queries into a work space maintained by `psql`. Try out these commands:

```

mydb=> SELECT version();
                                         version
-------------------------------------------------------------------​-----------------------
 PostgreSQL 18.6 on x86_64-pc-linux-gnu, compiled by gcc (Debian 4.9.2-10) 4.9.2, 64-bit
(1 row)

mydb=> SELECT current_date;
    date
------------
 2016-01-07
(1 row)

mydb=> SELECT 2 + 2;
 ?column?
----------
        4
(1 row)
```

The `psql` program has a number of internal commands that are not SQL commands. They begin with the backslash character, “`\`”. For example, you can get help on the syntax of various PostgreSQL SQL commands by typing:

```

mydb=> \h
```

To get out of `psql`, type:

```

mydb=> \q
```

and `psql` will quit and return you to your command shell. (For more internal commands, type `\?` at the `psql` prompt.) The full capabilities of `psql` are documented in [psql](/reference/reference-client/app-psql.md). In this tutorial we will not use these features explicitly, but you can use them yourself when it is helpful.

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/tutorial-accessdb.html)（英文原文，待翻譯）


---

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