Question

我只需要选择没有Room_IDs为NULL的实例的Status。

例如：

TABLE_A

  Room_Id   Status    Inspection_Date
  -----------------------------------
    1        NULL        5/15/2015
    2        occupied    5/21/2015
    2        NULL        1/19/2016
    1        occupied   12/16/2015
    4        NULL        3/25/2016
    3        vacant      8/27/2015
    1        vacant      4/17/2016
    3        vacant     12/12/2015
    3        vacant      3/22/2016
    4        vacant       2/2/2015
    4        vacant      3/24/2015

我的结果应如下所示：

  Room_Id  Status  Inspection_Date
  -----------------------------------
    3       vacant      8/27/2015
    3       vacant     12/12/2015
    3       vacant      3/22/2016

因为Room_ID'3'没有Status为NULL的实例

Answer 1

试试这个：

 SELECT *
 FROM Table1 
 WHERE Room_ID NOT IN 
 (
   SELECT DISTINCT Room_ID
   FROM Table1
   WHERE Status IS NULL
   )

子查询返回一个唯一的房间ID列表，这些房间ID在某一时间具有NULL状态。外部查询查看该列表，并说＆＃34;返回*其中room_ID不是子查询中的那个。

如果你想在SQL Fiddle中尝试它，这里是Schema：

CREATE TABLE Table1
    (Room_ID int, Status varchar(8), Inspection_Date datetime)
;

INSERT INTO Table1
    (Room_ID, Status, Inspection_Date)
VALUES
    (1, NULL, '2015-05-15 00:00:00'),
    (2, 'occupied', '2015-05-21 00:00:00'),
    (2, NULL, '2016-01-19 00:00:00'),
    (1, 'occupied', '2015-12-16 00:00:00'),
    (4, NULL, '2016-03-25 00:00:00'),
    (4, 'vacant', '2015-08-27 00:00:00'),
    (1, 'vacant', '2016-04-17 00:00:00'),
    (3, 'vacant', '2015-12-12 00:00:00'),
    (3, 'vacant', '2016-03-22 00:00:00'),
    (4, 'vacant', '2015-02-02 00:00:00'),
    (4, 'vacant', '2015-03-24 00:00:00'),
    (2, NULL, '2015-05-22 00:00:00')
;

Answer 2

如何做的快速示例：

DECLARE @tTable TABLE(
Room_Id INT,
Status VARCHAR(20),
Inspection_Date DATETIME)

INSERT INTO @tTable VALUES 
 (1, NULL, '5/15/2015'),
 (1,NULL,        '5/15/2015'),
 (2,'occupied',  '5/21/2015'),
 (2,NULL,        '1/19/2016'),
 (1,'occupied',  '12/16/2015'),
 (4,NULL,        '3/25/2016'),
 (3,'vacant',    '8/27/2015'),
 (1,'vacant',    '4/17/2016'),
 (3,'vacant',    '12/12/2015'),
 (3,'vacant',    '3/22/2016'),
 (4,'vacant',    '2/2/2015'),
 (4,'vacant',    '3/24/2015')

 SELECT * FROM @tTable T1
  WHERE Room_Id NOT IN (SELECT Room_ID FROM @tTable WHERE Status IS NULL)

给予：

Room_Id |   Status |    Inspection_Date         |
-------------------------------------------------
3       |   vacant |    2015-08-27 00:00:00.000
3       |   vacant |    2015-12-12 00:00:00.000
3       |   vacant |    2016-03-22 00:00:00.000

Answer 3

作为Hashman的替代方案，我更倾向于使用not exists而不是not in来进行这些类型的查询。

创建一些测试数据

请注意，我对所有内容保持相同的日期，因为这不是问题的必要条件。

create table #table_a (
    Room_Id int,
    Status varchar(32),
    Inspection_Date date);

insert #table_a (Room_Id, Status, Inspection_Date)
    values
        (1, null, getdate()),
        (2, 'occupied', getdate()),
        (2, null, getdate()),
        (1, 'occupied', getdate()),
        (4, null, getdate()),
        (3, 'vacant', getdate()),
        (1, 'vacant', getdate()),
        (3, 'vacant', getdate()),
        (3, 'vacant', getdate()),
        (4, 'vacant', getdate()),
        (4, 'vacant', getdate());

查询

select *
from #table_a t1
where not exists (
    select *
    from #table_a t2
    where t1.Room_Id = t2.Room_Id
        and Status is null);

结果

Room_Id     Status                           Inspection_Date
----------- -------------------------------- ---------------
3           vacant                           2016-06-17
3           vacant                           2016-06-17
3           vacant                           2016-06-17

Answer 4

您可以使用CTE和NOT EXIST，如下面的代码

WITH    bt
      AS ( SELECT   RoomId ,
                    Status,
                    Inspection_Date
           FROM     dbo.Table_1
         )
SELECT  *
FROM    bt AS a
WHERE   NOT EXISTS ( SELECT 1
                     FROM   bt
                     WHERE  bt.RoomId = a.RoomId
                            AND bt.Status IS NULL );

T-SQL：条件NULL删除

4 个答案: