DELETE a1, a2 FROM t1 AS a1 INNER JOIN t2 ASa2WHERE a1.id=a2.id;DELETE FROM a1, a2 USING t1 AS a1 INNER JOIN t2 ASa2WHERE a1.id=a2.id;

这两个SQL语句都是用于从两个表`t1`和`t2`中删除相关的行，基于它们之间的关联。第一种语法：

DELETE a1, a2 FROM t1 AS a1 INNER JOIN t2 AS a2 WHERE a1.id = a2.id;

这意味着它会同时删除`t1`和`t2`表中`id`字段相等的行，`a1`和`a2`是别名，表示来自`t1`和`t2`的行。

第二种语法：

DELETE FROM a1, a2 USING t1 AS a1 INNER JOIN t2 AS a2 WHERE a1.id = a2.id;

这种形式的`DELETE`通常不太常见，因为`USING`关键字通常用于JOIN操作，而不是直接删除操作。不过，如果解释成是想通过JOIN然后删除匹配行的话，它也表达的是同样的意思。

然而，需要注意的是，直接在`FROM`或`USING`列表中列出要删除的表可能会导致误解，因为在标准的SQL语法中，`DELETE`通常只涉及单个表，除非是在事务上下文中执行多表联合删除。在实际应用中，建议明确指定每个表的操作，如：

DELETE a1 FROM t1 INNER JOIN t2 ON t1.id = t2.id WHERE t1.id = a2.id;
DELETE a2 FROM t1 INNER JOIN t2 ON t1.id = t2.id WHERE t1.id = a2.id;