Access 支持三表或三表以上的 JOIN 操作，但是要加括号，一层一层 JOIN 下去。

例如：
SELECT * FROM (aa LEFT JOIN bb ON aa.a = bb.a ) LEFT JOIN cc ONcc.a = bb.a;

这里需要注意一个问题，在使用join语句查询时，也可以加多个条件，不过要用括号括起来，

如：
    错误的例子：SELECT * FROM (cc LEFT JOIN aa ON aa.a=cc.a) LEFT JOIN bb ON bb.a=aa.a AND aa.b=bb.b 会报错。

LEFT JOIN ON后面如果有多个条件时应该用括号括起来就不会出错了

    正确的写法：SELECT * FROM (aa LEFT JOIN bb ON aa.a=bb.a) LEFT JOIN cc ON(bb.a=cc.a and bb.b=cc.b)

我的例子：
1、SELECT * FROM URL as a LEFT OUTER JOIN MobileAfter as b  ON a.URL = b.URL

2、SELECT * FROM (URL as a LEFT OUTER JOIN MobileAfter as b  ON a.URL= b.URL)  LEFT OUTER JOIN MobileBefore as c ONc.URL=a.URL

3、SELECT * INTO Ttable1 FROM ((((URL as a

LEFT OUTER JOIN MobileAfter as b  ON a.URL=b.URL)

LEFT OUTER JOIN MobileBefore as c ON c.URL=a.URL)

LEFT OUTER JOIN TeleCOM      as d ON d.URL=a.URL)

LEFT OUTER JOIN UniCOM        as e ON e.URL=a.URL)