Mybatis之trim标签的使用

1、trim标签

<trim prefix="" suffix="" suffixOverrides="" prefixOverrides=""></trim>

2、参数说明
prefix：给trim标签内sql语句加上前缀
suffix：给trim标签内sql语句加上后缀
prefixOverrides：去除多余的前缀内容，如：prefixOverrides=“OR”，去除trim标签内sql语句多余的前缀"OR"
suffixOverrides：去除多余的后缀内容，如：suffixOverrides="，"，去除trim标签内sql语句多余的后缀"，"
3、demo
1、prefixOverrides

SELECT count(1)
FROM xxl_job_group AS t
<trim prefix="WHERE" prefixOverrides="AND | OR" >
    <if test="appname != null and appname != ''">
        AND t.app_name like CONCAT(CONCAT('%', #{appname}), '%')
    </if>
    <if test="title != null and title != ''">
        AND t.title like CONCAT(CONCAT('%', #{title}), '%')
    </if>
</trim>

2、suffixOverrides

<update id="updateUser" parameterType="map">
    update user
    <trim prefix="set" suffixOverrides="," suffix="where id = #{id}">
        <if test="username!=null and username!=''">username= #{username},</if>
        <if test="paeeword!=null and paeeword!=''">paeeword= #{paeeword},</if>
    </trim>
</update>