mybaits trim用法

prefix : 给<trim>包裹的sql语句加上前缀.

suffix : 给<trim>包裹的sql语句加上后缀.

prefixOverrides: 如果<trim>包裹的sql语句是空语句（经常出现在 if 判断为否的情况下）,取消指定的前缀，如where.

suffixOverrides: 如果<trim>包裹的sql语句是空语句（经常出现在 if 判断为否的情况下）,取消指定的后缀，如and | or. 逗号等

<!-- 新增-->
<insert id="save" parameterType="com.yp.api.qa.model.QuestionTemplate" keyProperty="id">
   insert into yp_qa.q_question_template
   <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="cateid != null">
         cateid,
      </if>
      <if test="title != null">
         title,
      </if>
      <if test="author != null">
         author,
      </if>
      <if test="type != null">
         type,
      </if>
      <if test="img != null">
         img,
      </if>
      <if test="video != null">
         video,
      </if>
      <if test="music != null">
         music,
      </if>
      <if test="hydesc != null">
         hydesc,
      </if>
      <if test="uid != null">
         uid,
      </if>
         createtime,
      <if test="tags != null">
         tags,
      </if>
      <if test="accountid != null">
         accountid,
      </if>
   </trim>
   <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="cateid != null">
         #{cateid},
      </if>
      <if test="title != null">
         #{title},
      </if>
      <if test="author != null">
         #{author},
      </if>
      <if test="type != null">
         #{type},
      </if>
      <if test="img != null">
         #{img},
      </if>
      <if test="video != null">
         #{video},
      </if>
      <if test="music != null">
         #{music},
      </if>
      <if test="hydesc != null">
         #{hydesc},
      </if>
      <if test="uid != null">
         #{uid},
      </if>
         now(),
      <if test="tags != null">
         #{tags},
      </if>
      <if test="accountid != null">
         #{accountid},
      </if>
   </trim>
</insert>