PHP循环记录非常慢

Question

I'm using PDO. So I have a statement that prepares a query to select a bunch of records. Example:

   //select duplicates
   $stmt = $this->db->prepare('SELECT Name COUNT( * ) AS CNT
            FROM  `Test`
            GROUP BY Name
            HAVING CNT > 1');

   $stmt2 = $this->db->prepare('SELECT * FROM Test2 WHERE TName = ?');

Note that I do need all data selected, not certain columns. The table contains 5k records, sometimes more. I need to select all 5k records and for each of them I need to execute another query to select something else.

   $arr = array();
   while ($row = $stmt->fetch(DB::FETCH_ASSOC)) {
       $stmt2->execute($row['Name']);
       $arr[] = $stmt2->fetchAll(DB::FETCH_ASSOC);
   }

I know I can use joins but for my case joins will not work, because I need to loop through the data and execute stmt2 for each stmt1 row.

When I run this it takes up to 10-15 minutes which I can't allow, I need it to be faster. Can anyone tell me what the problem is? 5k records does not seem that much to loop through.

      STMT1 returns up to 5.5k records

I need data for each duplicate returned:

Answer 1

Joins won't work? HIGHLY HIGHLY doubtful:

SELECT test2.*, count(test.name) AS cnt
FROM test
LEFT JOIN test2 ON test2.id = test.id
GROUP BY test.name
HAVING (cnt > 1)

another try, given the OP's troubles:

SELECT *
FROM test2
WHERE name IN (
   SELECT DISTINCT name
   FROM test
   GROUP BY name
   HAVING (count(*) > 1)
)