Mysql 如何查询最小值？
表 PTest 结构结构如下

PCode PCount
7 3
8 2
9 3
10 4
11 2

查询结果是 
PCode PCount
8 2

规则是：先考虑PCount最小，再考虑PCode最小
（注：PCode和PCount都是无序的，Pcode 唯一）

------解决方案--------------------
SELECT * from PTest WHERE PCode=(SELECT min(PCode) FROM PTest WHERE PCount=(SELECT min(PCount) from PTest))

经验证可以。
------解决方案--------------------
select pcode,pcount from ptest where pcount=(select min(pcount) from ptest) order by pcode limit 1

估计应该可以，没测试过。
------解决方案--------------------

SQL code

SELECT * from PTest WHERE PCode=(SELECT min(PCode) FROM PTest WHERE PCount=(SELECT min(PCount) from PTest)) and PCount=(select min(PCount) from PTest)

------解决方案--------------------
select *
from ptest
order by pcount,pcode limit 1