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hello guys,
i've always made my own programing but i've now hit a bit of a problem with mySQL and php.
i have two tables:
citys: id_city, city_name
events: id_event, id_city, event
how can i select only the cities that have events registered, but i want to have them displayed only once in a list.
Mike -
select distinct city_name from
citys inner join
events on events.id_city = citys.id_city
I can't remember if mysql has a distinct command or not, but I'm sure it does. -
I'm not sure if joins or subqueries are more efficient on MySQL, so you could also try:
SELECT `city_name`
FROM `citys`
WHERE `id_city` IN (SELECT DISTINCT `id_city` FROM `events`); -
I've usually found that sub queries are less efficient than joins, depending on the tables and the number of joins. for something like this, i'd say a join is better.
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just wonderful guys, i'm sticking with sub queries for the time beeing :)
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