mybatis trim标签

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mybatis的trim标签一般用于动态sql语句中去除多余的and关键字，逗号等

以下是trim标签中涉及到的属性：

案例

1. trim实现insert into ()values()

<insert id="insert" parameterType="InfoStudent">
    insert into info_student
    <trim prefix="(" suffix=")" suffixOverrides=",">
        <if test="name != null">name,</if>
        <if test="sex != null">sex,</if>
        <if test="portrait != null">portrait,</if>
    </trim>
    <trim prefix="values(" suffix=")" suffixOverrides=",">
        <if test="name != null">#{name},</if>
        <if test="sex != null">#{sex},</if>
        <if test="portrait != null">#{portrait},</if>
    </trim>
</insert>

2. trim实现where

<trim prefix="where" prefixOverrides="and|or">
    <if test="sex != null">and sex = #{sex}</if>
    <if test="name != null">and name like concat("%",#{name},"%")</if>
    <if test="classId != null">and class_id = #{classId}</if>
    <if test="grade != null">and grade = #{grade}</if>
</trim>

3. trim实现set

<trim prefix="set" suffixOverrides=",">
    <if test="name != null">name = #{name},</if>
    <if test="sex != null">sex = #{sex},</if>
    <if test="school != null">school = #{school},</if>
    <if test="grade != null">grade = #{grade},</if>
    <if test="major != null">major = #{major},</if>
    <if test="classId != null">class_id = #{classId},</if>
    <if test="portrait != null">portrait = #{portrait,jdbcType=VARCHAR},</if>
    <if test="editTime != null">edit_time = #{editTime,jdbcType=TIMESTAMP}</if>
</trim>