I would like to modify my question:
I am wondering in which examples joins are still making sense and not just unecessary complicating things. I know it depends on many factors, so I will give 2 real examples:
1.
I have tables cities and users. Does it make sense to use for a search int together with join instead of varchar? Does it make any huge difference?
Code:
SELECT userId FROM users WHERE cityName LIKE '%searchterm%'
vs
PHP Code:
SELECT userId FROM users
INNER JOIN on cities users.cityId=cities.cityId
WHERE cities.cityName LIKE '%searchterm%'
2.
In both cases I have tables users and memberships. The difference is that in first case, I there is extra field in user table, a field membership. "Golden" users are displayed in almost every page, so this query is very often.
PHP Code:
SELECT userId FROM users ORDER BY membership
vs
PHP Code:
SELECT userId FROM users
INNER JOIN memberships ON users.userId=memberships.userId
ORDER BY memberships.membership
Tnx!
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