比如：
SELECT * FROM tb_school WHERE id=(SELECT MAX(id) FROM tb_school WHERE status =1)
上面语句属于一般复杂语句，可以在generator生成的代码上扩展，扩展方式，我记录在后面，对于比这还要复杂的，还是得手写。
扩展参考http://www.mybatis.org/generator/generatedobjects/extendingExampleClass.html
扩展的方式就是继承自动生成的Example class，然后使用它
public class Max_schoolExample extends Tb_schoolExample {
public static class ExtendedCriteria extends Tb_schoolExample.Criteria {
public Criteria andMaxStatusEquals() {
StringBuffer sb = new StringBuffer("id=(SELECT MAX(id) FROM tb_school WHERE status =1)");
addCriterion(sb.toString());
return this;
}
}
public ExtendedCriteria createExtendedCriteria() {
ExtendedCriteria criteria = new ExtendedCriteria();
if (oredCriteria.size() == 0) {
oredCriteria.add(criteria);
}
return criteria;
}
}