使用case语句更新

Question

给出一张表:

ColumnPosition, ColumnName
   Col 1,          NULL
   Col 2,          NULL
   Col 3,          NULL

我想ColumnName根据ColumnPosition的预定义值映射进行更新.

例如:
如果ColumnPosition ='Col 1',则将ColumnName更新为'Name'如果ColumnPosition ='Col 3',则将ColumnName更新为'Address'

如何使用CASE语句完成此操作？

Answer 1

我认为你的意思是,UPDATE而不是INSERT:

UPDATE MyTable
SET ColumnName = CASE WHEN ColumnPosition = 'Col 1' THEN 'Name'
                      WHEN ColumnPosition = 'Col 3' THEN 'Address'
                      -- ... the rest of your conditions
                      ELSE -- put your default value here
                 END

Answer 2

您可以设置地图然后进行连接,而不是做一堆案例陈述

With Map as 
(
    SELECT       'Col 1' ColumnPosition , 'Name' as ColumnName
    UNION SELECT 'Col 3' , 'Address'
 )
UPDATE Table1 
SET Table1.ColumnName = Map.ColumnName
FROM
  table1  
  INNER JOIN MAP 
  ON Table1.ColumnPosition = Map.ColumnPosition;

DEMO