目标效果：根据in中元素的顺序返回结果

查询id为（2，4，1，3）的数据，并按此顺序返回

第一次尝试

select id, name from tb_shop where id in (2, 4, 1, 3);

期待效果

实际效果

正确的语句

select id, name from tb_shop where id in (2, 4, 1, 3) order by field(id, 2, 4, 1, 3);

项目中实现

方法一：自定义mapper.xml

mapper.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.hmdp.mapper.ShopMapper">

    <select id="queryShopAndSortByIds" resultType="com.hmdp.entity.Shop" parameterType="java.util.List">
        SELECT *
		FROM tb_shop
		WHERE id IN <foreach collection="shopIds" item="shopId" open="(" separator="," close=")"> #{shopId} </foreach>
		ORDER BY field(id, <foreach collection="shopIds" item="shopId" separator=","> #{shopId} </foreach>)
    </select>
    
</mapper>

mapper

package com.hmdp.mapper;

import com.hmdp.entity.Shop;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import org.apache.ibatis.annotations.Param;

import java.util.List;

public interface ShopMapper extends BaseMapper<Shop> {
    List<Shop> queryShopAndSortByIds(@Param("shopIds") List<Long> shopIds);
}

impl

List<Long> ids = new ArrayList<>(list.size());
List<Shop> shops = getBaseMapper().queryShopAndSortByIds(ids);

方法二：利用last()拼接order by field(id, id1, id2, id3…)的sql语句

List<Long> ids = new ArrayList<>(list.size());
String idStr = StrUtil.join(",", ids);
List<Shop> shops = lambdaQuery().in(Shop::getId, ids).last("ORDER BY FIELD(id," + idStr + ")").list();