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前言:

Mybatis的xml文件编写动态SQL是从mapper中获取传入的参数,但是如果是嵌套的子查询中,子查询动态SQL所需的参数不能像常规的那样直接从mapper中获取, 因为嵌套子查询中能获取的传参仅能来源于主查询中的结果, 如下文所示,即如何去解决这一问题

一、实体类

1、主类

import io.swagger.v3.oas.annotations.media.Schema;
import lombok.*;
import java.time.LocalDateTime;
import java.util.List;@Schema(description = "返回结果实体 Response VO")
@Data
@EqualsAndHashCode(callSuper = true)
@ToString(callSuper = true)
public class MainDataRespVO extends MainDataBaseVO {@Schema(description = "主键ID")private Long id;@Schema(description = "创建时间")private LocalDateTime createTime;@Schema(description = "子类详情列表")private List<SubDataRespVO> subDataList;
}

2、子类

import io.swagger.v3.oas.annotations.media.Schema;
import lombok.*;
import java.time.LocalDateTime;@Schema(description = "管理后台 - 子类实体信息 Response VO")
@Data
@EqualsAndHashCode(callSuper = true)
@ToString(callSuper = true)
public class SubDataRespVO extends SubDataBaseVO {@Schema(description = "主键ID")private Long subDataId;@Schema(description = "创建时间"D)private LocalDateTime createTime;
}

二、Mapper

List<MainDataRespVO> getMainDataList( @Param("localDateStart") String localDateStart,@Param("localDateEnd") String localDateEnd,@Param("shiftType") String shiftType,@Param("userId") Long userId);

三、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="xxx.MainDataMapper"><resultMap id="selectShiftDateList" type="xxx.MainDataRespVO"><id property="id" column="id"/><result property="workDate" column="work_date"/><result property="createTime" column="create_time"/><collection property="subDataList"javaType="list"ofType="xxx.vo.SubDataRespVO"select="selectSubDataList"column="{id=id, shiftType=shiftType, userId=userId}"></collection></resultMap><resultMap id="selectSubDataListMap" type="xxx.vo.SubDataRespVO"><result property="subDataId" column="id"/><result property="createTime" column="create_time"/><result property="userName" column="userName"/><result property="shiftType" column="shift_type"/><result property="userId" column="user_id"/><result property="shiftDateId" column="shift_date_id"/></resultMap><select id="selectSubDataList" resultMap="selectSubDataListMap">selectt2.id,t2.shift_date_id,t2.shift_type,t2.create_time,t2.user_idfrom sub_data t2where t2.main_data_id = #{id} and t2.deleted = 0<if test="shiftType!=null and shiftType != ''">and t2.shift_type = #{shiftType}</if><if test="userId!=null and userId != ''">and t2.user_id =  #{userId}</if>order by t2.create_time asc</select><select id="getMainDataList" resultMap="selectMainDataList">selectt1.id,t1.work_date,t1.create_time,#{shiftType} as shiftType,  <!-- 将外部参数作为常量列 -->#{userId} as userId        <!-- 将外部参数作为常量列 -->from main_data t1where t1.deleted = 0<if test="localDateStart!=null and localDateStart != ''">and t1.work_date >=  #{localDateStart}</if><if test="localDateEnd!=null and localDateEnd != ''">and #{localDateEnd} >= t1.work_date</if>order by t1.work_date asc</select></mapper>

四、详解

如下图所示,将mapper中需要传入子查询中的动态SQL参数,放到主查询的查询列表中去,取别名,别名即是传入到子查询中的动态SQL参数