/**
* Prepares a fragment of SQL to be used within a query.
* This supports both [field] = [value]|[placeholder] or just [value]|[placeholder]
*
* @param string $field The field name to be used, set to null if it's not needed
* @param string $placeholder The placeholder name to be used, set to null if a value is specified instead
* @param string $value The value to be used, set to null if a placeholder is specified instead
* @param Driver $driver Database driver, used to quote field names
* @param bool $is_for_nulls if true, we treat NULL different, otherwise use '=' only ( for UPDATE )
*
* @return string
*/
private static function prepareClause($field, $placeholder, $value, Driver $driver, $is_for_nulls = true)
{
$rhs = $placeholder === null ? $value : $placeholder;
if ($field === null) {
return $rhs;
}
// If the value is NULL, we need to use IS NULL, rather than =.
$operator = $is_for_nulls && $value === null ? 'IS' : '=';
return "{$driver->getQuotedName($field)} {$operator} {$rhs}";
}
