两个表a，b
a中字段为：id,name
b中字段为:id,email,address
查询语句：select a.*,b.* from a left join b on a.id=b.id
结果为：
id name sex id address email
----------- -------------------------------------------------- -------------------------------------------------- ----------- -------------------------------------------------- -
1 zy male 1 beijing zyip@qq.com
1 zy male 1 American zyip@msn.com
2 zk male 2 beijing zk@qq.com
2 zk male 2 nanjing zk@sina.com.cn
(4 row(s) affected)
问题，如果在left join语句中只取出与附表第一条记录联合的结果如何做？即主表数据只和附表第一条联合，其余忽略，例如下列结果：
id name sex id address email
----------- -------------------------------------------------- -------------------------------------------------- ----------- -------------------------------------------------- ---------------
1 zy male 1 beijing zyip@qq.com
2 zk male 2 beijing zk@qq.com