在 MySQL (8.0.17) 中将行转换为单列

Question

I tried to search posts, without any result either, maybe I didn't use the right words.

I need a solution in MySQL (8.0.17).

I have a table (called country ) with 4 columns:

1. Code
2. Name
3. Continent
4. Region

And these are the rows

+------+-------------+---------------+---------------------------+
| Code | Name        | Continent     | Region                    |
+------+-------------+---------------+---------------------------+
| ABW  | Aruba       | North America | Caribbean                 |
| AFG  | Afghanistan | Asia          | Southern and Central Asia |
| AGO  | Angola      | Africa        | Central Africa            |
| AIA  | Anguilla    | North America | Caribbean                 |
| ALB  | Albania     | Europe        | Southern Europe           |
+------+-------------+---------------+---------------------------+

I need do a select it will return

+----------------------------+
| Contents                   |
+----------------------------+
| ABW                        |                
| Aruba                      |        
| North America              |  
| Caribbean                  |                  
| AFG                        |   
| Afghanistan                |  
| Asia                       |           
| Southern and Central Asia  |
| AGO                        |
| Angola                     |    
| Africa                     |         
| Central Africa             |             
| AIA                        |   
| Anguilla                   |     
| North America              |  
| Caribbean                  |                  
| ALB                        |   
| Albania                    |      
| Europe                     |         
| Southern Europe            |
+----------------------------+

Also I want to keep all 4 columns of one record together.

DROP TABLE IF EXISTS `country`;
CREATE TABLE `country` (
    `id` INT(11) NOT NULL AUTO_INCREMENT,
    `Code` CHAR(3) NOT NULL,
    `Name` CHAR(52) NULL DEFAULT NULL,
    `Continent` VARCHAR(50) NULL DEFAULT NULL,
    `Region` CHAR(26) NULL DEFAULT NULL,
    PRIMARY KEY (`id`)
)
COLLATE='latin1_swedish_ci'
ENGINE=InnoDB
;

    
    -- ----------------------------
    -- Records of country
    -- ----------------------------
    INSERT INTO `country` (`id`, `Code`, `Name`, `Continent`, `Region`) VALUES (1, 'ABW', 'Aruba', 'North America', 'Caribbean');
INSERT INTO `country` (`id`, `Code`, `Name`, `Continent`, `Region`) VALUES (2, 'AFG', 'Afghanistan', 'Asia', 'Southern and Central Asia');
INSERT INTO `country` (`id`, `Code`, `Name`, `Continent`, `Region`) VALUES (3, 'AGO', 'Angola', 'Africa', 'Central Africa');
INSERT INTO `country` (`id`, `Code`, `Name`, `Continent`, `Region`) VALUES (4, 'AIA', 'Anguilla', 'North America', 'Caribbean');
INSERT INTO `country` (`id`, `Code`, `Name`, `Continent`, `Region`) VALUES (5, 'ALB', 'Albania', 'Europe', 'Southern Europe');

Answer 1

You can use UNION ALL to select all of them and if you have an auto increment primary key id .

SELECT txt 
FROM (SELECT id AS pk, `code` AS txt  FROM country
UNION ALL SELECT id, `name` FROM country
UNION ALL SELECT id, Continent FROM country
UNION ALL SELECT id, Region FROM country) AS t
ORDER BY t.pk;