Style guide ✨

Success

Although SQL is super flexible in how you write it, it's a good idea to stick to a consistent style.

This makes it easier for others to read your code which is especially important when you're working in a team or when you're sharing your code with others.

SQL style is a contentious topic...

Anyone who has written SQL for a little while will find the style that they like, and they'll typically want to stick to it (for better or worse) 😝

There are plenty of conflicting styles out there, so this guide is just to recommend the style for things that most people agree on.

Some general rules

Use consistent capitalisation

The capitalisation that you use for your column names and table names should match their case in the database.

For example, the AdventureWorks database uses Pascal case for its table names, so you should use Pascal case in your SQL:

/* Good */
SELECT FirstName, LastName
FROM Person.Person
WHERE BusinessEntityID < 5
;

/* Bad */
SELECT firstName, LASTNAME
FROM person.PERSON
WHERE businessentityid < 5
;

The capitalisation that you use for your SQL keywords (e.g. SELECT, FROM, WHERE) should be consistent, and should match the standards of your team (if you have one).

/* Good, if your team use uppercase */
SELECT FirstName, LastName
FROM Person.Person
WHERE BusinessEntityID < 5
;

/* Good, if your team use lowercase */
select FirstName, LastName
from Person.Person
where BusinessEntityID < 5
;

/* Bad */
SELECT FirstName, LastName
from Person.Person
WhEre BusinessEntityID < 5
;

Put new clauses on new lines

The main clauses (e.g. SELECT, FROM, WHERE) should be on new lines:

/* Good */
SELECT FirstName, LastName
FROM Person.Person
WHERE BusinessEntityID < 5
;

/* Bad */
SELECT FirstName, LastName FROM
Person.Person WHERE
BusinessEntityID < 5;

/* Bad */
SELECT FirstName, LastName FROM Person.Person WHERE BusinessEntityID < 5;

Put lists on indented new lines

For long lists of items (the length of "long" is contentious), put each item on a new line and indent it:

/* Good */
SELECT
    BusinessEntityID,
    PersonType,
    Title,
    FirstName,
    MiddleName,
    LastName
FROM Person.Person
WHERE BusinessEntityID < 20
  AND PersonType = 'EM'
  AND MiddleName IS NOT NULL
  AND EmailPromotion = 2
;

/* Bad */
SELECT BusinessEntityID, PersonType, Title, FirstName, MiddleName, LastName
FROM Person.Person
WHERE BusinessEntityID < 20 AND PersonType = 'EM' AND MiddleName IS NOT NULL AND EmailPromotion = 2
;