如何将 MYSQL 查询从“IN”更改为“INNER JOIN”？

Question

I have this code to search for a matching result in a MYSQL database:

$where[] = 'p.id IN (
    SELECT adcfvc.advert_id
      FROM #__koparent_advert_specific_fields_values AS adcfvc
     WHERE adcfvc.advert_id = p.id
       AND adcfvc.field_name = ' . $db->Quote($sf_key) . '
       AND ' . $db->Quote(JString::strtolower($sf_value)) . ' = adcfvc.field_value
)';

I want to change the above search query from using the "IN" operator to "INNER JOIN".

Knowing that I cannot change any of the database structure in anyway, just modify the above code.

Answer 1

I need to see the full query, but at a guess it is going to be:

LEFT JOIN adcfvc ON adcfvc.advert_id = $table.id

Where $table is the tablename of the first table.

Answer 2

Simply move the subquery to an inline view alias it and join on the keys.

and it appears you could eliminate the correlated sub-query in the where clause.

SELECT ...
FROM ...
LEFT JOIN (
    SELECT adcfvc.advert_id
      FROM #__koparent_advert_specific_fields_values AS adcfvc
     WHERE adcfvc.field_name = ' . $db->Quote($sf_key) . '
       AND ' . $db->Quote(JString::strtolower($sf_value)) . ' =
           adcfvc.field_value) B 
  on B.advert_Id = p.id

Answer 3

You'll need to post the rest of the query, because the able p is not shown. But what's odd about your question, is why you have an "in" at all. I think you just need to do the following:

  FROM #__koparent_advert_specific_fields_values AS adcfvc, whatever_table as p
 WHERE adcfvc.advert_id = p.id
   AND adcfvc.field_name = ' . $db->Quote($sf_key) . '
   AND ' . $db->Quote(JString::strtolower($sf_value)) . ' = adcfvc.field_value

)';