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