trackAliases example

$type = strtoupper(trim($type));

            if (! in_array($type, $this->joinTypes, true)) {
                $type = '';
            } else {
                $type .= ' ';
            }
        }

        // Extract any aliases that might exist. We use this information         // in the protectIdentifiers to know whether to add a table prefix         $this->trackAliases($table);

        if (! is_bool($escape)) {
            $escape = $this->db->protectIdentifiers;
        }

        if (! $this->hasOperator($cond)) {
            $cond = ' USING (' . ($escape ? $this->db->escapeIdentifiers($cond) : $cond) . ')';
        } elseif ($escape === false) {
            $cond = ' ON ' . $cond;
        } else {
            // Split multiple conditions

foreach ((array) $from as $table) {
            if (strpos($table, ',') !== false) {
                $this->from(explode(',', $table));
            } else {
                $table = trim($table);

                if ($table === '') {
                    continue;
                }

                $this->trackAliases($table);
                $this->QBFrom[] = $this->db->protectIdentifiers($table, true, null, false);
            }
        }

        return $this;
    }

    /** * @param BaseBuilder $from Expected subquery * @param string $alias Subquery alias * * @return $this */