src/Leevel/Database/Condition.php
protected function parseUnion(): string
    {
        if (empty($this->options['union'])) {
            return '';
        }

        $sql = '';

        if ($this->options['union']) {
            $options = count($this->options['union']);

            foreach ($this->options['union'] as $index => $value) {
                list($union, $type) = $value;

                if ($union instanceof self || $union instanceof Select) {
                    $union = $union->makeSql();
                }

                if ($index <= $options - 1) {
                    $sql .= "\n".$type.' '.$union;
                }
            }
        }

        return $sql;
    }
protected function parseUnion(): string
    {
        if (empty($this->options['union'])) {
            return '';
        }

        $sql = '';

        if ($this->options['union']) {
            $options = count($this->options['union']);

            foreach ($this->options['union'] as $index => $value) {
                list($union, $type) = $value;

                if ($union instanceof self || $union instanceof Select) {
                    $union = $union->makeSql();
                }

                if ($index <= $options - 1) {
                    $sql .= "\n".$type.' '.$union;
                }
            }
        }

        return $sql;
    }
解析 union 分析结果.

@return string