根据另一个表/列中的值插入一个表/列中的值

Question

I am trying to import a csv, unpivot the data and INSERT INTO product_attribute table.

I have a table called attributes

attribute_id	attribute_name	attribute_value
1	colour	black
2	colour	green
3	colour	blue
4	size	small
5	size	medium
6	size	large

I have a table called products

product_id	sku	qty
1	test3	13
2	test2	17
3	test1	5

I have a table called product_attribute which is linked between both tables above.

product_id	attribute_id

the csv data is as follows which imports into a temp folder called import .

sku	colour	size
test1	black	small
test2	green	large
test3	blue	medium

so far I have managed to unpivot the csv/table using the following query

SELECT sku, 'colour' attribute_name, colour attribute_value
FROM import
UNION ALL
SELECT sku, 'size' attribute_name, size attribute_value
FROM import
UNION ALL

the data then looks like this

sku	attribute_name	attribute_value
test1	colour	black
test2	colour	green
test3	colour	blue
test1	size	small
test2	size	large
test3	size	medium

I need to somehow add a INSERT INTO query with the unpivot query so the product_attribute table looks like the following

product_id	attribute_id
3	1
2	2
1	3
3	4
2	6
1	5

I believe a subquery would help me achieve this but I'm not sure how to put it together when the value is based on another column.

Any help greatly appreciated thankyou.

Answer 1

Use your code in a subquery and join it to the two tables using the common columns.

INSERT INTO product_attribute(product_id, attribute_id)
    SELECT p.product_id, a.attribute_id
    FROM (
        SELECT sku, 'colour' attribute_name, colour attribute_value
        FROM import
        UNION ALL
        SELECT sku, 'size' attribute_name, size attribute_value
        FROM import
        UNION ALL
    ) as u
    JOIN products p   USING(sku)
    JOIN attributes a USING(attribute_name, attribute_value)