容易忘记的关键写法

1、数据库方面
SQL SERVER:

select r.id,'R_'+ltrim(r.id),'R_'+CAST(r.id as VARCHAR(10)) from Role r where rolename is not null and description is not null

exists和not exists

引用

http://www.cnblogs.com/mytechblog/articles/2105785.html

2、js方面

  if(typeof(formId)=="undefined"){
		        	alert("值是多少!");
		        	return;
		        }

3、Mybatis方面

<!-- customized #s -->
  <resultMap id="resultMapId2" type="java.util.HashMap" >
      <result column="id" property="id" jdbcType="INTEGER" />
      <result column="roleId" property="roleId" jdbcType="INTEGER" />
      <result column="rolename" property="rolename" jdbcType="VARCHAR" />
  </resultMap>
  <!-- 查询所有的角色信息account -->
  <select id="selectRoleList" resultMap="resultMapId2">
   select r.id,'R_'+ltrim(r.id) as roleId,r.roleName from Role r 
   where rolename is not null and description is not null
       
  </select>
  
  <!-- customized #e -->

4、堆内存和非堆内存
http://blog.csdn.net/thunder0709/article/details/16855195