SELECT … FROM

The simplest query in SQL is called SELECT and extracts rows from a table. It is the language's "Hello, world", and you will use it in nearly every query you write for the rest of your life. The minimal syntax is:

SQL

SELECT <colonne>
FROM   <tabella>;

Read in English: "take these columns, from the given table". The SQL engine scans the table row by row and for each one returns only the requested columns.

All columns, or just some

SELECT * returns all the columns of the table. It is handy for exploring a new dataset, but in "real" code it is avoided: if tomorrow you add a column to the table, the query will silently return more data.
SELECT col1, col2 returns only the listed columns, in the order you write them. Changing the order changes the output.

SQL

-- Tutto, comodo per esplorare:
SELECT * FROM employees;

-- Solo le colonne che servono, nell'ordine deciso da te:
SELECT last_name, first_name, salary
FROM employees;

Whitespace, indentation, semicolons

SQL is forgiving with formatting: these three queries are identical to the engine:

SQL

SELECT first_name, last_name FROM employees;

SELECT first_name,last_name FROM employees;

SELECT
  first_name,
  last_name
FROM employees;

The third form is the one you will see most often in professional code: one column per line makes the diff more readable when you add or remove fields.

Try it

Exercise#sql.m1.l2.e1

Attempts: 0Loading…

Extract the first name (first_name) and last name (last_name) of all employees, in that order.

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Show hint

You need to list the two columns you want between SELECT and FROM, separated by a comma.

Solution available after 3 attempts

Review exercise

Exercise#sql.m1.l2.e2