条件:
select a.1, c.1,b.1
from a, b, c
where aID = bID and aID = cID
其中: aID在表a中是唯一值, bID在b表中有多个值, cID在c表中也有多个值.
问: aID = bID and aID = cID 会不会产生逻辑条件 cID = bID 而造成迪尔卡积连接??
而我做成二个联合语句,就会很快.
------解决方案--------------------
- SQL code
当然不会造成迪尔卡积。可以添加提示试试：select /*+leading(a)*/a.1, c.1,b.1 from a, b, c where aID = bID and aID = cID