SQL 查询内部连接与临时表

Question

我正在尝试使用此处显示的示例在临时表中设置值:SQL output: Is it possible to create a temporary output column?

我已经创建了我的初始表，我在其中使用列名作为新列值“operdesc”的总体。

这是我的工作表查询，我从中获得了所需的 COLUMN_NAME 值。我想添加一个临时列“OPERAND”:

SELECT     COLUMN_NAME, DATA_TYPE, 'OPERAND' AS TempField, 
                  CASE WHEN COLUMN_NAME = 'Street' THEN '=' WHEN COLUMN_NAME = 'Town' THEN 'CW' END AS OPERAND FROM         INFORMATION_SCHEMA.COLUMNS WHERE    (TABLE_SCHEMA = 'dbo') AND (TABLE_NAME = 'Customers') ORDER BY COLUMN_NAME

但是，我想更进一步，使用临时连接简化它。我按照这个例子:SQL output: Is it possible to create a temporary output column?但我挂断了我的剧本。这就是我所拥有的，但它不起作用，希望我很接近:

WITH XOperLU (xopername, xoperdesc)
 AS
 (
  SELECT xopername, CAST(xoperdesc AS VARCHAR(20))
    FROM (
          VALUES ('Street', 'SS'), 
                 ('Town', 'TW')                    
         ) AS XOperLU (xopername, xoperdesc)
 ) SELECT COLUMN_NAME as T1.COLUMN_NAME, DATA_TYPE as T1.DATA_TYPE, S1.xoperdesc AS Description FROM INFORMATION_SCHEMA.COLUMNS  AS T1 WHERE    (TABLE_SCHEMA = 'dbo') AND (TABLE_NAME = 'Clients') 
   INNER JOIN XOperLU AS S1
      ON S1.xopername = T1.COLUMN_NAME;

“客户”表是一个 View 。

非常感谢!

Answer 1

你几乎没问题，但你在列别名中使用了 T1 别名而不是列，最重要的是你在 JOIN 之前有 WHERE。这有效:

WITH XOperLU (xopername, xoperdesc)
 AS
 (
  SELECT xopername, CAST(xoperdesc AS VARCHAR(20))
    FROM (
          VALUES ('Street', 'SS'), 
                 ('Town', 'TW')                    
         ) AS XOperLU (xopername, xoperdesc)
 ) SELECT T1.COLUMN_NAME as COLUMN_NAME, T1.DATA_TYPE as DATA_TYPE, S1.xoperdesc AS Description FROM INFORMATION_SCHEMA.COLUMNS  AS T1 
   INNER JOIN XOperLU AS S1
      ON S1.xopername = T1.COLUMN_NAME
      WHERE    (TABLE_SCHEMA = 'dbo') AND (TABLE_NAME = 'Clients')

如果你想看到所有其他没有指定描述的列被设置为某些东西，例如'XX'，可以使用左连接:

WITH XOperLU (xopername, xoperdesc)
 AS
 (
  SELECT xopername, CAST(xoperdesc AS VARCHAR(20))
    FROM (
          VALUES ('Street', 'SS'), 
                 ('Town', 'TW')                    
         ) AS XOperLU (xopername, xoperdesc)
 ) SELECT T1.COLUMN_NAME as COLUMN_NAME, T1.DATA_TYPE as DATA_TYPE, ISNULL(S1.xoperdesc,'XX') AS Description FROM INFORMATION_SCHEMA.COLUMNS  AS T1 
   LEFT JOIN XOperLU AS S1
      ON S1.xopername = T1.COLUMN_NAME
      WHERE    (TABLE_SCHEMA = 'dbo') AND (TABLE_NAME = 'Clients')