Rules for writing queries

The Library's language has a few simple customs. Stick to them and your queries will always be readable.

The semicolon ends an order

We end every SQL command with a semicolon ";". It is a signal to the Library: "this is the whole order, you may run it".

SELECT * FROM autorzy;

The semicolon comes once, at the very end of the command - not after every column or after the shelf name.

Letter case

SQL keywords (SELECT, FROM, WHERE...) can be written in lower or upper case - it makes no difference to the Library. By convention, however, we write them in UPPERCASE to distinguish them from column and table names:

SELECT imie, nazwisko FROM czytelnicy;

Comments

Sometimes we want to leave a note in the margin of a scroll. A single-line comment starts with two dashes --:

-- This query shows all authors
SELECT * FROM autorzy;

Leave a space after the two dashes - MySQL needs it to recognize a comment. MySQL also understands comments that start with #, but in this land we stick to the standard --. The Library ignores comments - they are only for us, the scribes.

Whitespace

SQL does not care about spaces and new lines. These two queries are identical:

SELECT tytul FROM ksiazki;

SELECT tytul
FROM ksiazki;

We usually split longer queries across lines - it is more readable that way. Remember: the semicolon ends an order, UPPERCASE marks the keywords, and a -- comment is a note in the margin - every good scribe keeps these customs.