如果IN子查詢沒有行，如何返回所有行？

Question

下面是示例查詢

Select * 
    from tb.Users u 
where u.Approved = 1 
    and u.userID IN (SELECT us.UserID us 
         FROM tb.UserStatementes us 
         WHERE us.LogDate between date1 and date2) 

，我需要選擇那些在次IN子句但是如果子查詢未返回，我需要選擇所有用戶（即忽略IN子句）

Answer 1

Select * 
    from tb.Users u 
where u.Approved = 1 
    and (
    u.userID IN (SELECT us.UserID us 
         FROM tb.UserStatementes us 
         WHERE us.LogDate between date1 and date2 
         ) 
    or not exists (
     select 1 
      from tb.UserStatementes us 
      where us.LogDate between date1 and date2 
     ) 
    ) 

記錄所有用戶

Answer 2

Select * 
    from tb.Users u 
where u.Approved = 1 
    and (exists  (SELECT 1 
          FROM tb.UserStatementes us 
          WHERE us.LogDate between date1 and date2 
          AND us.USERID = u.USERID) 
     or not exists (SELECT 1 
          FROM tb.UserStatementes us 
          WHERE us.LogDate between date1 and date2) 
     )