mysql query for adding non existing rows with count zero - mysql

Question

"Table A" & "Table B" are my initial tables for the query. Result is the final table as shown in the following figure.Find Non-existing rows
Table A:
| Date | Name | Count |
|:----------:|:----:|:-----:|
| 01-01-2020 | A | 5 |
| 01-01-2020 | B | 15 |
| 02-01-2020 | B | 20 |
| 02-01-2020 | C | 15 |
| 02-01-2020 | D | 30 |
| 03-01-2020 | A | 30 |
| 03-01-2020 | D | 10 |
Table B:
| Name |
|:----:|
| A |
| B |
| C |
| D |
Result:
| Date | Name | Count |
|:----------:|:----:|:-----:|
| 01-01-2020 | A | 5 |
| 01-01-2020 | B | 15 |
| 01-01-2020 | C | 0 |
| 01-01-2020 | D | 0 |
| 02-01-2020 | A | 0 |
| 02-01-2020 | B | 20 |
| 02-01-2020 | C | 15 |
| 02-01-2020 | D | 30 |
| 03-01-2020 | A | 30 |
| 03-01-2020 | B | 0 |
| 03-01-2020 | C | 0 |
| 03-01-2020 | D | 10 |

Answer 1

cross join distinct dates from a to distinct id from b then left join a
drop table if exists t,t1;
create table t
(id varchar(1),dt date);
create table t1
(id varchar(1));
insert into t values
('a','2019-01-01'),('b','2019-01-01'),
('b','2019-02-01'),('d','2019-01-01'),
('c','2019-03-01');
insert into t1 values
('a'),('b'),('c'),('d');
select t3.id,t3.dt,t.id,t.dt
from
(
select distinct dt,s.id from t
cross join
(select distinct id from t1) s
) t3
left join t on t.id = t3.id and t.dt =t3.dt
order by t3.dt,t3.id;
+------+------------+------+------------+
| id | dt | id | dt |
+------+------------+------+------------+
| a | 2019-01-01 | a | 2019-01-01 |
| b | 2019-01-01 | b | 2019-01-01 |
| c | 2019-01-01 | NULL | NULL |
| d | 2019-01-01 | d | 2019-01-01 |
| a | 2019-02-01 | NULL | NULL |
| b | 2019-02-01 | b | 2019-02-01 |
| c | 2019-02-01 | NULL | NULL |
| d | 2019-02-01 | NULL | NULL |
| a | 2019-03-01 | NULL | NULL |
| b | 2019-03-01 | NULL | NULL |
| c | 2019-03-01 | c | 2019-03-01 |
| d | 2019-03-01 | NULL | NULL |
+------+------------+------+------------+
12 rows in set (0.05 sec)
PS - if you want solutions which are close to your model you should include table definitions and sample data as text in the question (which we can use) rather than links to images (which cannot use)