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To alter columns back and forth between numeric types and text,

we need upto 3 intermediate alters.
Corolary: MSSQL implicit conversions aren't transitive at all! :-)
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stronk7
stronk7 committed Aug 28, 2009
1 parent eb8f775 commit c402af03a84627fc596e782451c51c266e79b816
Showing with 55 additions and 1 deletion.
  1. +55 −1 lib/ddl/mssql_sql_generator.php
@@ -320,8 +320,62 @@ public function getAlterFieldSQL($xmldb_table, $xmldb_field) {
$results = $this->getDropDefaultSQL($xmldb_table, $xmldb_field);
}
/// Some changes of type require multiple alter statements, because mssql lacks direct implicit cast between such types
/// Here it is the matrix: http://msdn.microsoft.com/en-us/library/ms187928(SQL.90).aspx
/// Going to store such intermediate alters in array of objects, storing all the info needed
$multiple_alter_stmt = array();
$targettype = $xmldb_field->getType();
if ($targettype == XMLDB_TYPE_TEXT && $oldmetatype == 'I') { // integer to text
$multiple_alter_stmt[0] = new stdClass; // needs conversion to varchar
$multiple_alter_stmt[0]->type = XMLDB_TYPE_CHAR;
$multiple_alter_stmt[0]->length = 255;
} else if ($targettype == XMLDB_TYPE_TEXT && $oldmetatype == 'N') { // decimal to text
$multiple_alter_stmt[0] = new stdClass; // needs conversion to varchar
$multiple_alter_stmt[0]->type = XMLDB_TYPE_CHAR;
$multiple_alter_stmt[0]->length = 255;
} else if ($targettype == XMLDB_TYPE_TEXT && $oldmetatype == 'F') { // float to text
$multiple_alter_stmt[0] = new stdClass; // needs conversion to varchar
$multiple_alter_stmt[0]->type = XMLDB_TYPE_CHAR;
$multiple_alter_stmt[0]->length = 255;
} else if ($targettype == XMLDB_TYPE_INTEGER && $oldmetatype == 'X') { // text to integer
$multiple_alter_stmt[0] = new stdClass; // needs conversion to varchar
$multiple_alter_stmt[0]->type = XMLDB_TYPE_CHAR;
$multiple_alter_stmt[0]->length = 255;
$multiple_alter_stmt[1] = new stdClass; // and also needs conversion to decimal
$multiple_alter_stmt[1]->type = XMLDB_TYPE_NUMBER; // without decimal positions
$multiple_alter_stmt[1]->length = 10;
} else if ($targettype == XMLDB_TYPE_NUMBER && $oldmetatype == 'X') { // text to decimal
$multiple_alter_stmt[0] = new stdClass; // needs conversion to varchar
$multiple_alter_stmt[0]->type = XMLDB_TYPE_CHAR;
$multiple_alter_stmt[0]->length = 255;
} else if ($targettype == XMLDB_TYPE_FLOAT && $oldmetatype == 'X') { // text to float
$multiple_alter_stmt[0] = new stdClass; // needs conversion to varchar
$multiple_alter_stmt[0]->type = XMLDB_TYPE_CHAR;
$multiple_alter_stmt[0]->length = 255;
}
/// Just prevent default clauses in this type of sentences for mssql and launch the parent one
$results = array_merge($results, parent::getAlterFieldSQL($xmldb_table, $xmldb_field, NULL, true, NULL)); // Call parent
if (empty($multiple_alter_stmt)) { // Direct implicit conversion allowed, launch it
$results = array_merge($results, parent::getAlterFieldSQL($xmldb_table, $xmldb_field, NULL, true, NULL));
} else { // Direct implicit conversion forbidden, use the intermediate ones
$final_type = $xmldb_field->getType(); // Save final type and length
$final_length = $xmldb_field->getLength();
foreach ($multiple_alter_stmt as $alter) {
$xmldb_field->setType($alter->type); // Put our intermediate type and length and alter to it
$xmldb_field->setLength($alter->length);
$results = array_merge($results, parent::getAlterFieldSQL($xmldb_table, $xmldb_field, NULL, true, NULL));
}
$xmldb_field->setType($final_type); // Set the final type and length and alter to it
$xmldb_field->setLength($final_length);
$results = array_merge($results, parent::getAlterFieldSQL($xmldb_table, $xmldb_field, NULL, true, NULL));
}
/// Finally, process the default clause to add it back if necessary
if ($typechanged || $lengthchanged) {

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