有什么区别:
select t1.a1, t1.a2, t1.a3 from t1 cross join t2 where t1.a3 = t2.a1
和:
select t1.a1, t1.a2, t1.a3 from t1,t2 where t1.a3=t2.a1;
我可以互换使用吗?
mysql sql join cross-join
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