<select id="selectAuthor" resultType="Author">

        select * from author where sex = 'male'

        <if test="name != null">

            and name = #{name}

        </if>

    </select>

public List<Blog> selectBlogList(@Param("title") String title);

    <select id="selectBlogList" resultType="Blog">

        <bind name="titlePattern" value="'%' + title + '%'"/>

        select * from blog

        <where>

            <if test="title != null">

            and title like #{titlePattern}

            </if>

        </where>

    </select>

public List<Blog> selectBlogList(Blog blog);

<select id="selectBlogList" resultType="Blog">

        <bind name="titlePattern" value="'%' + _parameter.getTitle() + '%'"/>

        select * from blog

        <where>

            <if test="title != null">

            and title like #{titlePattern}

            </if>

        </where>

    </select>