4. Your First Query

Ok, the time has come! You've hopefully learned some background or refreshed your memory about what databases and SQL queries are, you've learned about the data we're using in this course, and it's time to write some queries for yourself!

A Simple Query

Let's first consider this simple query:

select 'Hello world!' as column_name

This is perhaps the simplest valid SQL query that can be written. Let's break down its component parts:

select tells the database that we want to execute a select statement, the result of which will be a table of some kind.
'Hello world!' wrapped in single quotes (') represents a literal string value, telling the database that we want everything between the single quotes to be treated as one continuous block of text, including the space between "Hello" and "world".
as column_name is a column alias telling the database that in the resulting table, the column name for our value, Hello world! should be column_name.

The result of this query will be a table with one column, column_name, and one row with the value Hello world! in that column.

The SQL Console

Below is an SQL console. You can type SQL queries into it and click "Submit", and you'll see the results of your query. The console is pre-populated with our simple select statement. The table below the console shows the result of our query.

No Results

Exercise 1: Modify the column alias

In the SQL console above, modify the query so that the column in our results is named my_column instead of column_name.

Exercise 2: Modify the value

In the SQL console above, modify the query so that the value in our results is Some new value instead of Hello world!.

Selecting multiple columns

So far, we've selected only one column. To select multiple columns, separate them with commas (,), like this:

select 
    'Hello world!' as first_column,
    'A second value' as second_column

Exercise 3: Add a column

In the SQL console above, modify the query so that we are selecting three values: A first value, A second value, and A third value with the columns named first_col, second_col, and third_col, respectively.

Notice that in some of these examples, I've put each of the columns in my select statement on a new line, and I've indented those lines. None of this is required; SQL is not sensitive to whitespace (extra spaces, tabs, line breaks). From the database's point of view, these two queries are identical:

select 'Something' as my_column

select
'Something'                as
my_column

Verify it for yourself by copy/pasting these queries into the SQL console or adding arbitrary whitespace to the queries you've written for the exercises above.

That said, for readability, it is common practice to place each column in your select statement on its own line and to use indentation and standard spacing to keep your queries easy to read. This doesn't matter much for simple queries like these, but will become very important as your queries grow.