在PHP中嵌套SQL查询

Question

Nesting SQL queries in PHP seems to be a bit of a worry. I needed a SQL query to populate select options in a drupal form and I used the following query.

SELECT data FROM webform_submitted_data WHERE nid = 1124 and cid = 4 and 
data not in (SELECT data FROM webform_submitted_data where nid = 1127 and cid = 11 group by data having COUNT(*) > 5)

This query work perfectly fine in phpMyAdmin, but when i try it out in a PHP code (given below) using db_query, it doesn't work (nothing is returned).

$array = array();
$sql = db_query("SELECT data FROM webform_submitted_data WHERE nid = 1124 and cid = 4 and data not in (SELECT data FROM webform_submitted_data where nid = 1127 and cid = 11 group by data having COUNT(*) > 5)");
while($row = db_fetch_object($sql)) {
$array[$row->data] = $row->data;
}
return $array;

Could anyone please correct me wrt what is wrong in my query or code ? Also, is there a way to implement this query in PHP ?

Answer 1

Is it worth point out that the two queries are not the same?

The first query, from phpMyAdmin, uses a AND NOT EXISTS (...subquery...).

The second uses and data not in (... subquery ... ).

Implies different behavior.

EDIT

In Drupal 6, the data field in webform_submitted_data is a mediumtext field. Using its content as a array key may not be a good idea. How about changing your query like this:

$array = array();
$sql = db_query("SELECT data FROM webform_submitted_data WHERE nid = 1124 and cid = 4    and data not in (SELECT data FROM webform_submitted_data where nid = 1127 and cid = 11   group by data having COUNT(*) > 5)");
while($row = db_fetch_object($sql)) {
    $array[] = $row->data;  // <<<<----- updated array push
}
return $array;

This way, you still get an array of results, but without having to use a long string value as key and possibly overwriting duplicates.