1、动态条件查询。<where>标签会智能地将第一个不为空的值对应语句前面的and删去。

<!--    动态条件查询-->
    <select id="selectByCondition" resultMap="brandResultMap">

        select *
        from tb_brand
        <where>
            <if test="status != null">and status = #{status}</if>
            <if test="companyName != null and companyName != ''">and company_name like #{companyName}</if>
            <if test="brandName != null and brandName != ''">and brand_name like #{brandName}</if>
        </where>
    </select>

 2、插入后返回主键。通过useGeneratedKeys和keyProperty的设置可以返回主键id，在测试代码中通过调用get方法得到。如brand.getId();

  <!--插入后返回主键-->
    <insert id="add" useGeneratedKeys="true" keyProperty="id">
        insert into tb_brand (brand_name, company_name, ordered, description, status)
        values (#{brandName}, #{companyName}, #{ordered}, #{description}, #{status});
    </insert>

 3、动态更新sql语句。在此案例中如果最后的status为空，<set>标签会智能地将不为空的最后一个值对应的语句后面的逗号删去。

    <!--动态更新sql语句-->
    <update id="update">
        update tb_brand
        <set>
            <if test="brandName != null and brandName != ''">
                brand_name = #{brandName},
            </if>
            <if test="companyName != null and companyName != ''">
                company_Name = #{companyName},
            </if>
            <if test="ordered != null">
                ordered = #{ordered},
            </if>
            <if test="description != null and description != ''">
                description = #{description},
            </if>
            <if test="status != null">
                status = #{status}
            </if>
            where id = #{id};
        </set>
    </update>

 4、批量删除动态语句。separator用于设置内部分隔符，open设置集合前字符，close设置集合后字符。

    <!--批量删除动态语句-->
    <delete id="deleteByIds">
        delete
        from tb_brand
        where id in
            <foreach collection="ids" item="id" separator="," open="(" close=")">
                #{id}
            </foreach>
            ;
    </delete>