关于tag标签系统的实现

实验室的项目，需要做对用户发布的主题进行打标签的功能，纠结甚久，实现思路如下：

一、数据库表的设计

1.tag表 

create table qa_tag(tag_id int primary key auto_increment,tag_name varchar(32) not null,tag_time timestamp not null default CURRENT_TIMESTAMP,refered_cnt int not null default 0,user_id int not null,unique (tag_name),constraint foreign key (user_id) references user_info(user_id));2.topic表  

create table qa_topic(topic_id int primary key auto_increment,topic_title varchar(128) not null,topic_body text not null,topic_time timestamp not null default CURRENT_TIMESTAMP,user_id int not null,tags varchar(128) not null default '');

 create table qa_tag_topic
(
record_id int primary key auto_increment,
tag_id int not null,
topic_id int not null,
constraint foreign key (tag_id) references qa_tag(tag_id),
constraint foreign key (topic_id) references qa_topic(topic_id)
);

1.用户创建主题时，给自己发布的主题打上了几个标签，点击提交

2.后台接受参数后，先把数据插入到qa_topic表中，获得了topicId；

3.把用户输入的标签转成数组，批量插入到数据库中，sql代码如下： 

<insert id="insertTags" parameterType="java.util.List">	    insert into qa_tag(tag_name,user_id) values	    <foreach collection="list" item="o" index="index" separator=",">	        (#{o.tagName},#{o.userId}) 	    </foreach>	    ON DUPLICATE KEY UPDATE refered_cnt = refered_cnt + 1;//如果有重复,则把tag的被引用数目+1	    alter table qa_tag auto_increment = 1//保证tagId的连续性</insert>

<select id="selectTagIds" resultType="com.tcm.dal.qaos.po.TagTopicMapPo">
  SELECT
      tag_id as tagId
  FROM qa_tag
  WHERE tag_name
      in
  <foreach item="item" index="index" collection="array"
      open="(" separator="," close=")">
        #{item}
  </foreach>
</select>

<insert id="insertTagTopicMap" parameterType="java.util.List">
    insert ignore into qa_tag_topic(tag_id,topic_id) values
    <foreach collection="list" item="o" index="index" separator=",">
        (#{o.tagId},#{o.topicId})
    </foreach>
</insert>