Solr 4 data one to many relationship settings

an article has many tags,
query using solr, each article has many tag's id in one tag_id column

core_name/conf/db-data-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<dataConfig>
    <dataSource name="db_source" type="JdbcDataSource"
                driver="com.mysql.jdbc.Driver"
                url="jdbc:mysql://192.168.1.1/db"
                user="xxx"
                password="xxx"
    />
    <document>
        <entity name="article"
                query="
SELECT id,title,content,
  DATE_FORMAT(
    a.updated_at,
    '%Y-%m-%dT%H:%i:%s.001Z'
  ) AS updated_time
FROM articles
"
                deltaImportQuery="
SELECT id,title,content,
  DATE_FORMAT(
    a.updated_at,
    '%Y-%m-%dT%H:%i:%s.001Z'
  ) AS updated_time
FROM articles
WHERE id= '${dataimporter.delta.id}'
                "
                deltaQuery="
SELECT id,title,content,
  DATE_FORMAT(
    a.updated_at,
    '%Y-%m-%dT%H:%i:%s.001Z'
  ) AS updated_time
FROM articles
WHERE updated_at > '${dataimporter.last_index_time}'
"
                transformer="HTMLStripTransformer,RegexTransformer,TemplateTransformer"
                dataSource="db_source"
        >
            <field column="updated_at" name="last_modified" />
            <entity name="tag"
                    query="
SELECT id AS tag_id
FROM tags WHERE article_id = '${article.id}'
"
                    deltaImportQuery="
SELECT id AS tag_id
FROM tags
WHERE id = '${dataimporter.delta.id}'
"
                    deltaQuery="
SELECT id AS tag_id
FROM tags
WHERE updated_at > '${dataimporter.last_index_time}'
"
                    transformer="HTMLStripTransformer,RegexTransformer,TemplateTransformer"
                    dataSource="db_source"
            >
                <field column="updated_at" name="last_modified" />
            </entity>
        </entity>
    </document>
</dataConfig>

core_name/conf/schema.xml

<?xml version="1.0" encoding="UTF-8" ?>
<schema name="demo" version="1.5">
    <field name="id" type="int" indexed="true" stored="true" required="true" multiValued="false" />
    <field name="title" type="string" indexed="true" stored="true" required="false" multiValued="false" />
    <field name="content" type="htmlStripChinese" indexed="true" stored="true" required="false" multiValued="false" />
    <field name="tag_id" type="int" indexed="true" stored="true" required="false" multiValued="true" />
    <field name="updated_time" type="tdate" indexed="true" stored="true" required="false" multiValued="false" />
    <field name="text_all" type="htmlStripChinese" indexed="true" stored="false" omitNorms="false" multiValued="true" />
    <uniqueKey>id</uniqueKey>

     <defaultSearchField>text_all</defaultSearchField>
   
   <copyField source="title" dest="text_all"/>
   <copyField source="content" dest="text_all"/>
</schema>