copy-kamanote/src/main/resources/mapper/QuestionMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.copykamanotes.mapper.QuestionMapper">

    <insert id="insert" useGeneratedKeys="true" keyProperty="questionId"
            parameterType="com.example.copykamanotes.model.entity.Question">
        INSERT INTO question (category_id, title, difficulty, exam_point)
        VALUES (#{categoryId}, #{title}, #{difficulty}, #{examPoint})
    </insert>

    <select id="findById" resultType="com.example.copykamanotes.model.entity.Question">
        SELECT *
        FROM question
        WHERE question_id = #{questionId}
    </select>

    <select id="findByIdBatch" resultType="com.example.copykamanotes.model.entity.Question">
        SELECT * FROM question
        WHERE
        <if test="questionIds != null and questionIds.size > 0">
            question_id IN
            <foreach collection="questionIds" item="questionId" open="(" separator="," close=")">
                #{questionId}
            </foreach>
        </if>
        <if test="questionIds == null or questionIds.size == 0">
            1 = 2 <!-- 当 questionIds 为空时，返回一个永远不成立的条件 -->
        </if>
    </select>

    <sql id="whereClause">
        <where>
            <if test="queryParam.categoryId != null">
                (category_id = #{queryParam.categoryId}
                OR category_id IN (
                    SELECT category_id
                    FROM category
                    WHERE parent_category_id = #{queryParam.categoryId}
                ))
            </if>
        </where>
    </sql>

    <select id="findByQueryParam" resultType="com.example.copykamanotes.model.entity.Question">
        SELECT *
        FROM question
        <include refid="whereClause"/>
        <choose>
            <when test="queryParam.sort == 'view'">
                ORDER BY view_count
            </when>
            <when test="queryParam.sort == 'difficulty'">
                ORDER BY difficulty
            </when>
            <otherwise>
                ORDER BY created_at
            </otherwise>
        </choose>
        <choose>
            <when test="queryParam.order == 'asc'">
                ASC
            </when>
            <when test="queryParam.order == 'desc'">
                DESC
            </when>
            <otherwise>
                ASC
            </otherwise>
        </choose>
        LIMIT #{limit} OFFSET #{offset}
    </select>

    <select id="findByKeyword" resultType="com.example.copykamanotes.model.entity.Question">
        SELECT *
        FROM question
        <choose>
            <when test="keyword != null">
                WHERE title LIKE CONCAT('%', #{keyword}, '%')
            </when>
            <otherwise>
                WHERE 1 = 2
            </otherwise>
        </choose>
    </select>

    <update id="update">
        UPDATE question
        <set>
            <if test="question.title != null">
                title = #{question.title},
            </if>
            <if test="question.difficulty != null">
                difficulty = #{question.difficulty},
            </if>
            <if test="question.examPoint != null">
                exam_point = #{question.examPoint},
            </if>
        </set>
        WHERE question_id = #{question.questionId}
    </update>

    <update id="incrementViewCount">
        UPDATE question
        SET view_count = view_count + 1
        WHERE question_id = #{questionId}
    </update>

    <select id="countByQueryParam" resultType="int">
        SELECT COUNT(*)
        FROM question
        <include refid="whereClause"/>
    </select>

    <delete id="deleteByCategoryId">
        DELETE
        FROM question
        WHERE category_id = #{categoryId}
    </delete>


    <delete id="deleteById">
        DELETE
        FROM question
        WHERE question_id = #{questionId}
    </delete>

    <delete id="deleteByCategoryIdBatch">
        <if test="categoryIds != null and categoryIds.size > 0">
            DELETE
            FROM question
            WHERE category_id IN
            <foreach collection="categoryIds" item="categoryId" open="(" separator="," close=")">
                #{categoryId}
            </foreach>
        </if>
        <if test="categoryIds == null or categoryIds.size == 0">
            DELETE FROM question WHERE 1 = 0
        </if>
    </delete>
</mapper>