MySQL Update Table from Another Table Recursively - mysql

Question

I have two tables, table1 and table2, where table1 is updated to fill in missing (null) values based on matching fields in table2 to create a more complete table1.
I have tried numerous queries such as
UPDATE table1 INNER JOIN table2...SET...
and
UPDATE table1 SET ... (SELECT)...
However my results are always incomplete. Note that I have a much larger dataset in both tables in terms of both columns and rows). I just used this as simpler example.
Rules:
1) The `keyword` from table2 looks for a match in `keyword` in table1 and must accept partial matches.
2) No values can be overwritten in table1 (update null values only)
3) The lookup order is per run_order in table2.
Specific example:
Table1:
|-----|-------------------------------|----------|-----|---------|-------|
|t1_id|keyword |category |month|age |skill |
|-----|-------------------------------|----------|-----|---------|-------|
| 1 |childrens-crafts-christmas |kids | | | |
| 2 |kids-costumes | | |tween | |
| 3 |diy-color-printable |printable | | |easy |
| 4 |toddler-halloween-costume-page | | | | |
|-----|-------------------------------|----------|-----|---------|-------|
Table2:
|-----|---------|---------|----------|-----|----------|-------|
|t2_id|run_order|keyword |category |month|age |skill |
|-----|---------|---------|----------|-----|----------|-------|
| 1 | 1 |children | | |4-11 yrs | |
| 2 | 2 |printable| | | |easy |
| 3 | 3 |costume |halloween | 10 |0-12 years| |
| 4 | 4 |toddler | | |1-3 years | |
| 5 | 5 |halloween|holiday | 10 | | |
|-----|---------|---------|----------|-----|----------|-------|
Result:
|-----|-------------------------------|----------|-----|---------|-------|
|t1_id|keyword |category |month|age |skill |
|-----|-------------------------------|----------|-----|---------|-------|
| 1 |childrens-crafts-christmas |kids | |4-11 yrs | |
| 2 |kids-costumes |halloween | 10 |tween | |
| 3 |diy-color-printable printable |printable | | |easy |
| 4 |toddler-halloween-costume-page |holiday | 10 |1-3 years| |
|-----|-------------------------------|----------|-----|---------|-------|
MySQL for schema and table data:
DROP TABLE IF EXISTS table1;
DROP TABLE IF EXISTS table2;
CREATE TABLE `table1` (
`t1_id` INT NOT NULL AUTO_INCREMENT,
`keyword` VARCHAR(200) NULL,
`category` VARCHAR(45) NULL,
`month` VARCHAR(45) NULL,
`age` VARCHAR(45) NULL,
`skill` VARCHAR(45) NULL,
PRIMARY KEY (`t1_id`));
CREATE TABLE `table2` (
`t2_id` INT NOT NULL AUTO_INCREMENT,
`run_order` INT NULL,
`keyword` VARCHAR(200) NULL,
`category` VARCHAR(45) NULL,
`month` INT NULL,
`age` VARCHAR(45) NULL,
`skill` VARCHAR(45) NULL,
PRIMARY KEY (`t2_id`));
INSERT INTO `table1` (`keyword`, `category`) VALUES ('childrens-crafts-christmas', 'kids');
INSERT INTO `table1` (`keyword`, `age`) VALUES ('kids-costumes', 'tween');
INSERT INTO `table1` (`keyword`, `category`, `skill`) VALUES ('diy-color-printable', 'printable', 'easy');
INSERT INTO `table1` (`keyword`) VALUES ('toddler-halloween-costume-page');
INSERT INTO `table2` (`run_order`, `keyword`, `age`) VALUES (1, 'children', '4-11 yrs');
INSERT INTO `table2` (`run_order`, `keyword`, `skill`) VALUES (2, 'printable', 'easy');
INSERT INTO `table2` (`run_order`, `keyword`, `category`, `month`, `age`) VALUES (3, 'costume', 'halloween', 10, '0-12 years');
INSERT INTO `table2` (`run_order`, `keyword`, `age`) VALUES (4, 'toddler', '1-3 years');
INSERT INTO `table2` (`run_order`, `keyword`, `category`, `month`) VALUES (5, 'halloween', 'holiday', 10);

Answer 1

You want to update empty values in table1 with the value in the corresponding column of the first matching record in table2, run_order wise. A typical solution is to use a combination of correlated subqueries to find the matching records in table2 and keep only the one with lowest run_order.
Here is a query that will update null categories with this logic:
update table1 t1
set category = (
select category
from table2 t2
where t2.run_order = (
select min(t22.run_order)
from table2 t22
where
t1.keyword like concat('%', t22.keyword, '%')
and t22.category is not null
)
)
where t1.category is null
This assumes that run_order is unique in table2 (which seems relevant in your use case).
You can extend the logic for more columns with coalesce(). Here is the solution for columns category and month:
update table1 t1
set
category = coalesce(
t1.category,
(
select category
from table2 t2
where t2.run_order = (
select min(t22.run_order)
from table2 t22
where
t1.keyword like concat('%', t22.keyword, '%')
and t22.category is not null
)
)
),
month = coalesce(
t1.month,
(
select month
from table2 t2
where t2.run_order = (
select min(t22.run_order)
from table2 t22
where
t1.keyword like concat('%', t22.keyword, '%')
and t22.month is not null
)
)
)
where t1.category is null or t1.month is null
Demo on DB Fiddle

Answer 2

You can use a join between the 2 tables using a like expression and the if nul() function to ensure you don't overwrite non null values.
UPDATE table1 t1
INNER JOIN table2 t2 ON t1.keyword like concat("%",t2.keyword,"%")
SET
t1.category = ifnull(t1.category,t2.category),
t1.age = ifnull(t1.age,t2.age),
t1.skill = ifnull(t1.skill,t2.skill);