sqlite create table from pdo resultset? - php

Question

Does anyone have or can point to a good example of creating sqlite in-memory table using php pdo where the table columns formats are gathered directly from a PDO query result?
My use case is that I'd like to use SQLite3 to store multiple resultsets from a number of queries (all the same column order etc) that are returned from a number of different databases. The end goal is to use SQLite to "reduce" the data for finalization.
I understand I could write a custom function for each query result, but my goal is to implement a universal solution, not needing to know the table structure, passing x homogenous resultsets (PDO::FETCH_ASSOC array results for example) and return a temporary SQLite table name to be able to query the UNION of the resultset(s) with SQLite before discarding the data.
It seems like this would be out on the internet somewhere and the SQLite website even alludes to this being a use case, but all my searches point to basic SQLite howtos on creating and querying...thanks in advance!

Answer 1

Since nobody replied, here is a rough effort. This is based on the db handle being mySQL, but it may be possible to ignore types and let sqlite do some magic. If so, see this link:
https://www.sqlite.org/datatype3.html
try{
$link = connectToDB_PDO();
$strSQL="select * from website.customers";
$mySth=$link->prepare($strSQL);
$meta=array();
$mySth->execute();
foreach(range(0, $mySth->columnCount() - 1) as $column_index){
$meta[] = $mySth->getColumnMeta($column_index);
}
$result=$mySth->fetchAll(PDO::FETCH_ASSOC);
// Create new database in memory
$memdb = new PDO('sqlite::memory:');
$memdb->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); // Set errormode to exceptions
$tablename='mytable';
$colnames=array(); // for the insert statement below
$tableSQL="CREATE TABLE $tablename ( ";
foreach($meta as $col){
$colnames[]=$col['name'];
$tableSQL.=" ".$col['name']. " ".$col['native_type']." ";
if(array_key_exists('flags',$col)){
foreach($col['flags'] as $flag){
switch($flag)
{
case 'not_null':
$tableSQL.=" NOT NULL ";
break;
case 'primary_key':
$tableSQL.=" PRIMARY KEY ";
break;
default:
} // end switch
} // end each flag
} // end if flags
$tableSQL.=", ";
} // end each column
$tableSQL=rtrim($tableSQL,", ");
$tableSQL.=")";
$memdb->exec($tableSQL);
$pragmaSQL="PRAGMA table_info($tablename)";
$st2=$memdb->prepare($pragmaSQL);
$st2->execute();
$pragres=$st2->fetchAll(PDO::FETCH_ASSOC);
$insert = "INSERT INTO $tablename (".implode(",",$colnames).") ".
"VALUES (:".implode(",:",$colnames).")";
$stmt = $memdb->prepare($insert);
foreach ($result as $row) {
$parms=array();
for($i=0;$i<count($colnames);$i++){
$parms[':'.$colnames[$i]]=$row[$colnames[$i]]; // Bind parameters to statement variables
}
$stmt->execute($parms);
}
$strSQL="SELECT sum(customers_id) FROM $tablename";
$sth=$memdb->prepare($strSQL);
$sth->execute();
$result2=$sth->fetchAll(PDO::FETCH_ASSOC);
foreach ($result2 as $m) {
echo print_r($m,true);
}
$memdb->exec("DROP TABLE $tablename");
$memdb = null;
} catch(PDOException $e) {
echo $e->getMessage();
error_log($e->getMessage());
}
I'm not sure if this is the best answer, but its a start - anxious to see other's input!