我有这样的SQL sentense最好的选择:
SELECT aps.*,(SELECT name FROM brands WHERE id=aps.brand) as brand FROM applications as aps
什么是做一个SQL在这种情况下
而这另一:
SELECT aps.*,brd.name as brand FROM applications as aps INNER JOIN brands as brd ON aps.brand=brd.id
两种查询结果是相等的,所以我猜这两者之间没有任何区别。但优化呢?
使用'解释你query'在mysql中,这将告诉ü更多.. –
带索引的加入比你的合作有关的查询更好,助相关子查询将运行forech相关记录 –