MySQL 8.0

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CREATE TABLE `clients_basses` (
   `id` INT(10) NOT NULL AUTO_INCREMENT,
   `name` VARCHAR(50) NULL DEFAULT NULL COLLATE 'utf8mb4_0900_ai_ci',
    PRIMARY KEY (`id`) USING BTREE
)COLLATE='utf8_general_ci' ENGINE=InnoDB AUTO_INCREMENT=2;
INSERT INTO `clients_basses` VALUES (1, 'База клиентов 1');
SELECT * FROM clients_basses;
CREATE TABLE `clients` (
   `id` INT(10) NOT NULL AUTO_INCREMENT,
   `base_id` INT(10) NOT NULL,
   `ctreated_at` TIMESTAMP NULL DEFAULT NULL,
   `updated_at` TIMESTAMP NULL DEFAULT NULL,
   PRIMARY KEY (`id`) USING BTREE,
   INDEX `FK_clients_clients_basses` (`base_id`) USING BTREE,
   CONSTRAINT `FK_clients_clients_basses` FOREIGN KEY (`base_id`) REFERENCES 
   `clients_basses` (`id`) ON UPDATE CASCADE ON DELETE CASCADE
) COLLATE='utf8mb4_0900_ai_ci' ENGINE=InnoDB AUTO_INCREMENT=2;
INSERT INTO `clients` VALUES (1, 1, '2021-03-18 20:45:18', '2021-03-18 20:45:20');
SELECT * FROM clients;
CREATE TABLE `client_fields` (
   `id` INT(10) NOT NULL AUTO_INCREMENT,
   `base_id` INT(10) NOT NULL,
   `client_id` INT(10) NOT NULL,
   `label` VARCHAR(255) NULL DEFAULT NULL COLLATE 'utf8mb4_0900_ai_ci',
   `key` VARCHAR(255) NULL DEFAULT NULL COLLATE 'utf8mb4_0900_ai_ci',
   PRIMARY KEY (`id`) USING BTREE,
   INDEX `FK_client_fields_clients_basses` (`base_id`) USING BTREE,
   INDEX `FK_client_fields_clients` (`client_id`) USING BTREE,
   CONSTRAINT `FK_client_fields_clients` FOREIGN KEY (`client_id`) REFERENCES 
   `clients` (`id`) ON UPDATE NO ACTION ON DELETE NO ACTION,
   CONSTRAINT `FK_client_fields_clients_basses` FOREIGN KEY (`base_id`) 
   REFERENCES `clients_basses` (`id`) ON UPDATE CASCADE ON DELETE CASCADE) COLLATE='utf8mb4_0900_ai_ci' ENGINE=InnoDB AUTO_INCREMENT=4;
INSERT INTO `client_fields` VALUES (1, 1, 1, 'Имя', 'name');
INSERT INTO `client_fields` VALUES (2, 1, 1, 'Телефон', 'phone');
INSERT INTO `client_fields` VALUES (3, 1, 1, 'Возраст', 'age');
SELECT * FROM client_fields;
CREATE TABLE `client_values` (
    `id` INT(10) NOT NULL AUTO_INCREMENT,
    `field_id` INT(10) NOT NULL,
    `base_id` INT(10) NULL DEFAULT NULL,
    `value` VARCHAR(255) NULL DEFAULT NULL COLLATE 'utf8mb4_0900_ai_ci',
    PRIMARY KEY (`id`) USING BTREE,
    INDEX `FK__client_fields` (`field_id`) USING BTREE,
    INDEX `FK_client_values_clients_basses` (`base_id`) USING BTREE,
    CONSTRAINT `FK_client_values_clients_basses` FOREIGN KEY (`base_id`) REFERENCES `clients_basses` (`id`) ON UPDATE NO ACTION ON DELETE NO ACTION,
    CONSTRAINT `FK__client_fields` FOREIGN KEY (`field_id`) REFERENCES `client_fields` (`id`) ON UPDATE NO ACTION ON DELETE NO ACTION
) COLLATE='utf8mb4_0900_ai_ci' ENGINE=InnoDB AUTO_INCREMENT=5;
INSERT INTO `client_values` VALUES (1, 1, 1, 'Роман');
INSERT INTO `client_values` VALUES (2, 2, 1, '991');
INSERT INTO `client_values` VALUES (3, 2, 1, '103');
INSERT INTO `client_values` VALUES (4, 3, 1, '26');
SELECT * FROM client_values;

id	name
1	База клиентов 1

id	base_id	ctreated_at	updated_at
1	1	2021-03-18 20:45:18	2021-03-18 20:45:20

id	base_id	client_id	label	key
1	1	1	Имя	name
2	1	1	Телефон	phone
3	1	1	Возраст	age

id	field_id	base_id	value
1	1	1	Роман
2	2	1	991
3	2	1	103
4	3	1	26