SELECT is where you pick the final columns that appear in the table the query outputs. Here’s the syntax:

SELECT expression_l [AS alias],
       expression_2 [AS alias2],
FROM ...

Some useful things YOU can do in a SELECT :

• Combine many columns with SQL expressions A few examples: CONCAT (first_name, ' ', last_name) DATE_TRUNC('month', created)

(This is PostgreSQL syntax for rounding date, other SQL dialects have different syntax)

• Alias an expression with AS

first_name || ' ' || last_name AS full_name is a mouthful! If you alias an expression with AS, you can use the alias elsewhere in the query to refer to that expression.

(|| is a concatenation operation)

SELECT first_name || ' ' || last_name AS full_name
FROM people
ORDER BY full_name desc

(full_name refers to first_name || ' ' || last_name)

• Select columns with SELECT *

When I’m starting to figure out a query, I’ll often write something like

SELECT * FROM some _ table LIMIT 10

just to quickly see what the columns in the table look like.