【thinkphp知识】thinkphp 使用union链式操作合并两个或多个 SELECT 语句的结果集，新增不存在的字段，并赋予默认值

Db::field('name')
   ->table('think_user_0')
   ->union(function($query){
    $query->field('name')->table('think_user_1');
     })
   ->union(function($query){
    $query->field('name')->table('think_user_2');
     })
   ->select();

$subQuery = Db::table('think_user')
    ->field('id,name')
    ->where('id','>',10)
    ->buildSql();

//全局搜索接口
public function search()
{
    $request = request()->post();
    $limit = $request['limit'] ?? 10;
    $title = $request['title'] ?? '';

    //菜单导航:1=新闻中心,2=网上办事,3=法规标准,4=协会专家,5=供应,6=采购
    $where = [];
    if ($title) $where['name'] = ['like', "%" . $title . "%"];
    $sql4 = DB::name("expert")->field("id, name, '' AS title, tags, '' AS url , FROM_UNIXTIME(createtime) as createtime, 4 AS menu")
        ->where($where)
        ->buildSql();
    $sql5 =DB::name("supply")->field("id, name, '' AS title, tags, '' AS url , FROM_UNIXTIME(createtime) as createtime, 5 AS menu")
        ->where($where)
        ->buildSql();

    $where = [];
    if ($title) $where['title'] = ['like', "%" . $title . "%"];
    $sql1 = DB::name("news")->field("id, '' AS name, title, tags, '' AS url , FROM_UNIXTIME(createtime) as createtime, 1 AS menu")
        ->where($where)
        ->buildSql();
    $sql2 = DB::name("work")->field("id, '' AS name, title, tags, url, FROM_UNIXTIME(createtime) as createtime, 2 AS menu")
        ->where($where)
        ->buildSql();
    $sql3 = DB::name("laws")->field("id, '' AS name, title, tags, '' AS url , FROM_UNIXTIME(createtime) as createtime, 3 AS menu")
        ->where($where)
        ->buildSql();
    $sql6 = DB::name("purchase")->field("id, '' AS name, title, tags, '' AS url, FROM_UNIXTIME(createtime) as createtime, 6 AS menu") 
        ->where($where);
    //合并
    $sql = $sql6->union([$sql1, $sql2, $sql3, $sql4, $sql5])->buildSql();
    $data = Db::table($sql.' a')->order("a.createtime desc")->paginate($limit);
        $this->success('获取成功', $data);
    }

Db::field('name')
    ->table('think_user_0')
    ->unionAll('SELECT name FROM think_user_1')
    ->unionAll('SELECT name FROM think_user_2')
    ->select();

Db::field('name')
    ->table('think_user_0')
    ->union(['SELECT name FROM think_user_1', 'SELECT name FROM think_user_2'], true)
    ->select();