sql优化要求不要写*,要把表名写全
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="usernp">
<sql id="columns">
id,name,addr,age
</sql>
<select id="ifsql" resultType="User">
select <include refid="columns"/> from user
where id={#id}
and name=#{name}
and addr=#{addr}
</select>
</mapper>
