动态SQL(choose, when, otherwise)

概要

1.读者在阅读博客前可以事先阅读MyBatis3.4官方文档
2.本篇博客用于解决在使用MyBatis3.4时可能出现的困惑

choose标签

1.先看一段MyBatis3.4官方文档的例子

<select id="findActiveBlogLike" resultType="Blog">
    SELECT * FROM BLOG WHERE state = ‘ACTIVE’
    <choose>
        <when test="title != null">
            AND title like #{title}
        </when>
        <when test="author != null and author.name != null">
            AND author_name like #{author.name}
        </when>
        <otherwise>
            AND featured = 1
        </otherwise>
    </choose>
</select>  

2.choose标签在使用时等价于java中的if else

if（...）{  
... 
}else if(...){  
...  
}else{  
...
}  

参考文档

http://blog.youkuaiyun.com/ABCD898989/article/category/6076264
http://blog.youkuaiyun.com/abcd898989/article/details/51222452