Import CSV to Update rows in table

Question

There are approximately 26K products (posts) and each product has meta values like this:

Answer 1

You can import the new data into another table (table2). Then update your primary table (table1) using a update with a sub-select:

UPDATE table1 t1 set 
  sale_price = (select meta_value from table2 t2 where t2.post_id = t1.product_id)
WHERE
  (select count(*) from table2 t2 where t1.product_id = t2.post_id) > 0

This is obviously a simplification and you will most likely need to constrain your query a little further.

Make sure to backup your full database before attempting. I recommend you work on a non-production database until the process works flawlessly.