DB rules Cheat Sheet by jasperdelaat

GOOD:

SELECT
projec­ts.name AS projec­t_name,
COUNT(­bac­kin­gs.id) AS backin­gs_­count
...


BAD:

SELECT
projec­ts.name projec­t_name,
COUNT(­bac­kin­gs.id) backin­gs_­count
...

GOOD:

SELECT
name,
goal
FROM projects AS projects
WHERE
country = 'US'
AND deadline >= '2015-­01-01'
...


BAD:

SELECT
name,
goal
FROM projects AS projects
WHERE country = 'US' AND deadline >= '2015-­01-01'
...

GOOD:

INNER JOIN backings AS backings ON ...
INNER JOIN users AS users ON ...
INNER JOIN locations AS locations ON ...
LEFT JOIN backer­_re­wards AS backer­_re­wards ON ...
LEFT JOIN ...


BAD:

LEFT JOIN backer­_re­wards AS backer­_re­wards ON backings
INNER JOIN users AS users ON ...
LEFT JOIN ...
INNER JOIN locations AS locations ON ...

GOOD:

SELECT
projec­ts.name AS projec­t_name,
COUNT(­bac­kin­gs.id) AS backin­gs_­count
FROM projects AS projects
INNER JOIN backings AS backings ON backin­gs.p­ro­ject_id = projec­ts.id
...


BAD:

SELECT
projec­ts.name AS projec­t_name,
COUNT(­bac­kin­gs.id) AS backin­gs_­count
FROM projects AS projects, backings AS backings
WHERE
backin­gs.p­ro­ject_id = projec­ts.id
...

GOOD:

SELECT
projec­ts.name AS projec­t_name,
COUNT(­bac­kin­gs.id) AS backin­gs_­count
FROM projects AS projects
INNER JOIN backings AS backings ON ...
INNER JOIN ...
LEFT JOIN backer­_re­wards AS backer­_re­wards ON ...
LEFT JOIN ...


BAD:

SELECT
projec­ts.name AS projec­t_name,
COUNT(­bac­kin­gs.id) AS backin­gs_­count
FROM projects AS projects
JOIN backings AS backings ON ...
LEFT JOIN backer­_re­wards AS backer­_re­wards ON ...
LEFT JOIN ...

GOOD:

CASE WHEN category = 'Art'
THEN backer_id
ELSE NULL
END


BAD:

CASE
WHEN category = 'Art'
THEN backer_id
ELSE NULL
END