这两种从多个表中选择数据的方法有什么区别。第一个不使用JOIN而第二个。哪一个是首选的方法?哪种方法最好加入mysql表?
方法1:
SELECT t1.a, t1.b, t2.c, t2.d, t3.e, t3.f
FROM table1 t1, table2 t2, table3 t3
WHERE t1.id = t2.id
AND t2.id = t3.id
AND t3.id = x
方法2:
SELECT t1.a, t1.b, t2.c, t2.d, t3.e, t3.f
FROM `table1` t1
JOIN `table2` t2 ON t1.id = t2.id
JOIN `table3` t3 ON t1.id = t3.id
WHERE t1.id = x
[内连接相比交叉连接的性能]可能的重复(http://stackoverflow.com/questions/670980/performance-of-inner-join-compared-to-cross-join) – soulmerge 2011-04-25 14:17:58