Question

我刚从朋友处得到这个问题。我有一张表，如下所示

DECLARE @table TABLE
(
ID INT IDENTITY(1,1) NOT NULL,
NAME VARCHAR(30),
SURNAME VARCHAR(30)
)

INSERT INTO @table(NAME, SURNAME)
VALUES('Mohit', 'Vaghadiya'),
      ('Paresh', 'Panchal'),
      ('Devid','Pietersen'),
      ('kapil','Soni')

===================================
| ID  |     NAME    |   SURNAME   |    
=================================
| 1   |   Mohit     |   Vaghadiya |
| 2   |   Paresh    |   Panchal   |
| 3   |   Devid     |   Pietersen |
| 4   |   kapil     |   Soni      |
===================================

我只想更新 ID ＆＃39; 1＆＃39;的 NAME 列值使用 ID 的 SURNAME ＆＃39; 3＆＃39;反之亦然我想更新 ID ＆＃39; 3＆＃39;的 SURNAME 列值使用 NAME ID ＆＃39; 1＆＃39;

输出

===================================
| ID  |     NAME    |   SURNAME   |    
===================================
| 1   |   Pietersen |   Vaghadiya |
| 2   |   Paresh    |   Panchal   |
| 3   |   Devid     |   Mohit     |
| 4   |   kapil     |   Soni      |
===================================

我知道我们可以这样做

DECLARE @name VARCHAR(30)

SELECT @name = SURNAME FROM @table WHERE ID = 3

UPDATE @table
SET SURNAME = (SELECT NAME FROM @table WHERE ID = 1)
WHERE ID = 3

UPDATE @table
SET NAME = @name
WHERE ID = 1

但是，有没有办法通过只执行一个 UPDATE 语句来实现呢？

Answer 1

您可以使用两个case表达式，一个用于名称，另一个用于姓氏：

UPDATE @table
  SET name =
       case
         when ID = 1 then (SELECT SURNAME FROM @table WHERE ID = 3)
         else name
       end,

     surname =
       case
         when ID = 3 then (SELECT NAME FROM @table WHERE ID = 1)
         else surname
       end
WHERE ID in (1, 3)

<强> sqlFiddle

Answer 2

您可以使用与第一组表中的第1行和另一表中的第3行匹配的条件来连接表。您可以使用x+y-x = y和x+y-y = x这一事实，即表达式(3+1) - ID计算另一个ID，即t1.ID = 4 - t2.ID。

然后您需要更新值的条件，以便您只更改每条记录中的正确值：

update t1
set
  NAME = case t1.ID when 1 then t2.SURNAME else t1.NAME end,
  SURNAME = case t1.ID when 3 then t2.NAME else t1.SURNAME end
from
  MyTable t1
  inner join MyTable t2 on t2.ID = 4 - t1.ID
where
  t1.ID in (1,3)

演示：http://sqlfiddle.com/#!6/83257/11

Answer 3

这应该适合你：

DECLARE @name VARCHAR(30)

SELECT @name = SURNAME FROM @table WHERE ID = 3

UPDATE @table
SET SURNAME = CASE 
        WHEN ID = 3
            THEN (SELECT NAME FROM @table WHERE ID = 1)
        ELSE SURNAME
        END
    ,NAME = CASE 
        WHEN ID = 1
            THEN @name
        ELSE NAME
        END
WHERE id IN (1,3)

只需使用CASE语句来处理这两种情况，然后先更新SURNAME列，然后更新NAME列。

Answer 4

UPDATE @table
SET    SURNAME = CASE
                   WHEN ID = 3 THEN (SELECT NAME
                                     FROM   @table
                                     WHERE  ID = 1)
                   ELSE SURNAME
                 END,
       NAME = CASE
                WHEN ID = 1 THEN (SELECT SURNAME
                                  FROM   @table
                                  WHERE  ID = 3)
                ELSE NAME
              END
WHERE  id IN ( 1, 3 )

如何使用一个UPDATE语句更新两个列值，反之亦然

4 个答案: