SELECT in practice

You already know SELECT, FROM and the semicolon. Now we will practice combining them across different shelves. Everything you need you have already learned - here it is about fluency.

A single column

To take just one field, give its name after the SELECT keyword:

SELECT nazwa FROM kategorie;

The Library will return a list of section names only - without the identifiers or other fields.

Several columns

We list columns separated by commas. The order in which you give them is the order in which they appear in the result:

SELECT imie, nazwisko, email FROM czytelnicy;

This returns three fields for each reader - first name, last name and e-mail, in exactly that order.

The primary key is a column too

id is an ordinary column - you can retrieve it just like any other:

SELECT id, tytul FROM ksiazki;

The result shows the catalog number and the title of every book - in exactly the order in which you listed the columns.

Different shelves, the same syntax

The pattern is always the same: SELECT columns FROM table;. Only the shelf name and the list of fields change:

SELECT data_wypozyczenia FROM wypozyczenia;

You get only the borrowing dates - nothing about who took which book, because you did not ask for those fields.

In the same way you take fields from the authors shelf - this time three of them, separated by commas:

SELECT imie, nazwisko, kraj FROM autorzy;

The more queries you write, the more this rhythm will become second nature. It is the foundation of the entire journey ahead!