10.2.output

+-------+--------+------+-----+---------+-------+
| Field | Type   | Null | Key | Default | Extra |
+-------+--------+------+-----+---------+-------+
| a     | bit(1) | YES  |     | NULL    |       |
| b     | bit(1) | YES  |     | NULL    |       |
| c     | bit(1) | YES  |     | NULL    |       |
+-------+--------+------+-----+---------+-------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
| 0    |     | NULL |
| 0    | NULL | 1    |
+------+------+------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
| 0    | 1    | NULL |
| 0    | 1    | 1    |
+------+------+------+
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| a     | tinyint(1) | YES  |     | NULL    |       |
| b     | tinyint(1) | YES  |     | NULL    |       |
| c     | tinyint(1) | YES  |     | NULL    |       |
+-------+------------+------+-----+---------+-------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    0 |    1 | NULL |
|    0 | NULL |    1 |
+------+------+------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    0 |    1 | NULL |
|    0 |    1 |    1 |
+------+------+------+

10.5.output

+-------+--------+------+-----+---------+-------+
| Field | Type   | Null | Key | Default | Extra |
+-------+--------+------+-----+---------+-------+
| a     | bit(1) | YES  |     | NULL    |       |
| b     | bit(1) | YES  |     | NULL    |       |
| c     | bit(1) | YES  |     | NULL    |       |
+-------+--------+------+-----+---------+-------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
| 0    |    1 | NULL |
| 0    | NULL | 1    |
+------+------+------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
| 0    | 1    | NULL |
| 0    | 1    | 1    |
+------+------+------+
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| a     | tinyint(1) | YES  |     | NULL    |       |
| b     | tinyint(1) | YES  |     | NULL    |       |
| c     | tinyint(1) | YES  |     | NULL    |       |
+-------+------------+------+-----+---------+-------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    0 |    1 | NULL |
|    0 | NULL |    1 |
+------+------+------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    0 |    1 | NULL |
|    0 |    1 |    1 |
+------+------+------+

docker-compose.yml

version: '3.6'

services:
  dbexp:
    image: ${IMAGE:-mariadb:10.5}
    container_name: dbexp
    environment:
      MYSQL_ALLOW_EMPTY_PASSWORD: 1
      MYSQL_ROOT_PASSWORD: ''
    ports:
      - 3306:3306
    volumes:
      - ./:/app

script.sql

create schema if not exists `test`;

use test;

drop table if exists test;
create table test(
    a bit,
    b bit,
    c bit
);

insert into test(a,b,c) values(0, 1, NULL);

show columns from test.test;

# a couple of union examples
select a, b, c from test
union select 0, NULL, 1;

select a, b, c from test
union select 0, 1, 1;

# CONVERT TO TINYINT

alter table test.test modify column a boolean default NULL NULL;
alter table test.test modify column b boolean default NULL NULL;
alter table test.test modify column c boolean default NULL NULL;
show columns from test.test;

# same union examples as above
select a, b, c from test
union select 0, NULL, 1;

select a, b, c from test
union select 0, 1, 1;

x_gory_details.txt

$ IMAGE=mariadb:10.2 docker-compose up -d
$ docker exec dbexp bash -c 'mysql --table < /app/script.sql'
+-------+--------+------+-----+---------+-------+
| Field | Type   | Null | Key | Default | Extra |
+-------+--------+------+-----+---------+-------+
| a     | bit(1) | YES  |     | NULL    |       |
| b     | bit(1) | YES  |     | NULL    |       |
| c     | bit(1) | YES  |     | NULL    |       |
+-------+--------+------+-----+---------+-------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
| 0    |     | NULL |
| 0    | NULL | 1    |
+------+------+------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
| 0    | 1    | NULL |
| 0    | 1    | 1    |
+------+------+------+
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| a     | tinyint(1) | YES  |     | NULL    |       |
| b     | tinyint(1) | YES  |     | NULL    |       |
| c     | tinyint(1) | YES  |     | NULL    |       |
+-------+------------+------+-----+---------+-------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    0 |    1 | NULL |
|    0 | NULL |    1 |
+------+------+------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    0 |    1 | NULL |
|    0 |    1 |    1 |
+------+------+------+
$
$
$
$ docker-compose down
$ IMAGE=mariadb:10.5 docker-compose up -d
$ docker exec dbexp bash -c 'mysql --table < /app/script.sql'
+-------+--------+------+-----+---------+-------+
| Field | Type   | Null | Key | Default | Extra |
+-------+--------+------+-----+---------+-------+
| a     | bit(1) | YES  |     | NULL    |       |
| b     | bit(1) | YES  |     | NULL    |       |
| c     | bit(1) | YES  |     | NULL    |       |
+-------+--------+------+-----+---------+-------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
| 0    |    1 | NULL |
| 0    | NULL | 1    |
+------+------+------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
| 0    | 1    | NULL |
| 0    | 1    | 1    |
+------+------+------+
+-------+------------+------+-----+---------+-------+
| Field | Type       | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+-------+
| a     | tinyint(1) | YES  |     | NULL    |       |
| b     | tinyint(1) | YES  |     | NULL    |       |
| c     | tinyint(1) | YES  |     | NULL    |       |
+-------+------------+------+-----+---------+-------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    0 |    1 | NULL |
|    0 | NULL |    1 |
+------+------+------+
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    0 |    1 | NULL |
|    0 |    1 |    1 |
+------+------+------+
$