MySQL5.7高级函数：JSON_ARRAYAGG和JSON_OBJECT的使用

前置准备

DROP TABLE IF EXISTS `t_user`;
CREATE TABLE `t_user`
(
    `id`                     bigint(20)                                                              NOT NULL,
    `name`                   varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci            NOT NULL                 DEFAULT ''          COMMENT '姓名',
	`relative_ids`	         json															         NOT NULL		                              COMMENT '亲人',
	`friend_ids`	         varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci			 NOT NULL		          DEFAULT ''          COMMENT '朋友',
    `sex`                    int                                                                     NOT NULL                 DEFAULT 0           COMMENT '性别 1:男,2:女',
    `object_id`              bigint(20)                                                              NOT NULL                 DEFAULT 0           COMMENT '对象id',
    PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB
  CHARACTER SET = utf8mb4
  COLLATE = utf8mb4_general_ci COMMENT = '用户表';

INSERT INTO `t_user` VALUES (1, '张伟', '[]', '3,4', 1, 5);
INSERT INTO `t_user` VALUES (2, '李明', '[4, 5]', '', 1, 0);
INSERT INTO `t_user` VALUES (3, '王强', '[]', '', 1, 4);
INSERT INTO `t_user` VALUES (4, '雨婷', '[]', '', 2, 3);
INSERT INTO `t_user` VALUES (5, '蕾蕾', '[]', '', 2, 1);

数据分析

1、王强和雨婷、张伟和蕾蕾互为情侣

2、王强和雨婷都是张伟的朋友

3、雨婷和蕾蕾都是李明的亲人  

需求实现

1、查询出“李明”的个人信息以及他的亲人信息

SELECT
	usr.id,
	usr.NAME,
	usr.relative_ids,
	(
	SELECT
		JSON_ARRAYAGG( JSON_OBJECT( 'id', relative.id, 'name', relative.NAME ) ) 
	FROM
		t_user relative 
	WHERE
		relative.id IN ( SELECT relative_ids.id FROM JSON_TABLE ( usr.relative_ids, '$[*]' COLUMNS ( id BIGINT PATH '$' ) ) AS relative_ids ) 
	) AS relative_infos,
	usr.friend_ids,
	usr.sex,
	usr.object_id 
FROM
	t_user usr 
WHERE
	id = 2

2、查询出“张伟”的个人信息以及他的朋友信息

SELECT
	usr.id,
	usr.NAME,
	usr.relative_ids,
	(
	SELECT
		JSON_ARRAYAGG( JSON_OBJECT( 'id', friend.id, 'name', friend.NAME ) ) 
	FROM
		t_user friend 
	WHERE
		FIND_IN_SET( friend.id, usr.friend_ids ) > 0 
	) AS friend_infos,
	usr.friend_ids,
	usr.sex,
	usr.object_id 
FROM
	t_user usr 
WHERE
	id = 1

3、查询出“有对象”的个人信息以及他(她)的对象信息

SELECT
	usr.id,
	usr.NAME,
	usr.relative_ids,
	( SELECT JSON_OBJECT( 'id', object.id, 'name', object.NAME ) FROM t_user object WHERE object.id = usr.object_id ) AS object_info,
	usr.friend_ids,
	usr.sex,
	usr.object_id 
FROM
	t_user usr 
WHERE
	usr.object_id != 0