Question

The following query isn’t efficient and I need to make it run much faster.

id  select_type table   type    possible_keys   key key_len ref rows    Extra
1   PRIMARY sob_datas   ALL sob_form_id,sob_form_id_2   NULL    NULL    NULL    365990  Using where
2   DEPENDENT SUBQUERY  sub_sob_datas   ALL sob_form_id,sob_form_id_2   NULL    NULL    NULL    365990  Using where

How can I optimize this query? sob_field_value is a text field

I’m pulling fields in each of these forms that have different values.

SELECT
                sob_datas.id,
                sob_datas.sob_field_name,
                sob_datas.sob_field_value
            FROM sob_datas
            WHERE sob_form_id = '.$proof['SobForm']['id'].' AND
            EXISTS(
                    SELECT
                        sub_sob_datas.id
                    FROM sob_datas AS sub_sob_datas
                    WHERE sub_sob_datas.sob_form_id = '.$original['SobForm']['id'].' AND
                    sub_sob_datas.sob_field_name = sob_datas.sob_field_name AND
                    sub_sob_datas.sob_field_value != sob_datas.sob_field_value
            )

I should also point out, I’m going to update only the changed fields with the new values

Answer 1

It is hard to wrap your head around what is trying to be done here 🙂 So hopefully I caught the point and this is what you are looking for / works. If not let me know and I will try and figure it out.

A bit of test data may help the process along (5-10 rows or so) and what is expected to be fetched from those rows. But here is my shot at it:

    SELECT
            sob_datas.id,
            sob_datas.sob_field_name,
            sob_datas.sob_field_value
    FROM sob_datas sd 
        JOIN sob_datas ssd ON sd.sob_field_name = ssd.sob_field_name
    WHERE sd.sob_form_id = '.$proof['SobForm']['id'].' 
        AND sd.sob_field_value != ssd.sob_datas.sob_field_value