在MyBatis的XML映射文件中＜trim＞元素所有场景下的完整使用示例代码

<update id="updateUser" parameterType="com.mybatis.domain.vo.UpdateUser">
    update user
    <trim prefix="SET" suffixOverrides=",">
        <if test="userName != null">user_name= #{userName},</if>
        <if test="email != null">email = #{email},</if>
        <if test="age != null">age = #{age},</if>
    </trim>
    where id= #{id}
</update>

<select id="selectUser" parameterType="map" resultType="User">
    SELECT * FROM user
    <trim prefix="WHERE" prefixOverrides="AND |OR ">
        <if test="userName != null">AND user_name = #{userName}</if>
        <if test="email != null">AND email = #{email}</if>
        <if test="age != null">AND age = #{age}</if>
    </trim>
</select>

<insert id="insertUser" parameterType="User">
    INSERT INTO user
    <trim prefix="(" suffix=")" suffixOverrides=",">
        <if test="userName != null">user_name,</if>
        <if test="email != null">email,</if>
        <if test="age != null">age,</if>
    </trim>
    VALUES
    <trim prefix="(" suffix=")" suffixOverrides=",">
        <if test="userName != null">#{userName},</if>
        <if test="email != null">#{email},</if>
        <if test="age != null">#{age},</if>
    </trim>
</insert>

<sql id="dynamicColumns">
    <trim prefix="SELECT" suffixOverrides=",">
        <if test="includeId">id,</if>
        <if test="includeName">name,</if>
        <if test="includeAge">age,</if>
    </trim>
    FROM user
</sql>
<select id="selectUsers" parameterType="map" resultType="User">
    <include refid="dynamicColumns"/>
    <trim prefix="WHERE" prefixOverrides="AND |OR ">
        <if test="userName != null">AND user_name = #{userName}</if>
        <if test="email != null">AND email = #{email}</if>
        <if test="age != null">AND age = #{age}</if>
    </trim>
</select>