first-query.md

Postgres by Example: First Query

Your first step is to run a query against PostgreSQL. You don't need any tables—you can evaluate simple expressions. This confirms that the server is running and that you can connect with psql.

What you'll learn:

• How to run a SQL file with psql
• Running a minimal SELECT with no table
• Checking PostgreSQL version

-- Simplest query: no tables, just a literal
SELECT 1;

-- Check your PostgreSQL version
SELECT version();

SELECT 1 returns a single row with one column; the value is the integer 1. SELECT version() calls a built-in function and returns your server version string.

To run this file from the repository root:

$ psql -f source/first-query.sql postgres
 ?column?
----------
        1
(1 row)

                                                    version
------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 16.x on x86_64-pc-linux-gnu, compiled by gcc ...
(1 row)

Your version string will vary. If you see output like above, you're set up correctly.

Tip: If you omit the database name, psql uses your default (often your OS username). To use the postgres database explicitly: psql -f source/first-query.sql postgres.

Try it: Run psql -f source/first-query.sql and confirm you see one row for SELECT 1 and one for version().

Source: first-query.sql

Next: psql Basics

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