带有临时表的 SQL 查询内部联接

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，在该表中我使用列名来填充新的值列“operdesc”。

这是我获得所需 COLUMN_NAME 值的工作表查询。我想添加一个临时列“操作数”：

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，并使用临时连接对其进行简化。我遵循了这个例子：SQL output: Is it possible to create a temporary output column?，但我挂断了我的脚本。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”表是一个视图。

提前非常感谢！

Answer 1

您几乎没问题，但您在列别名而不是列中使用了 T1 别名，最重要的是，您在 JOIN 之前使用了 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')

如果您想查看所有其他未指定要设置描述的列，例如'XX'，你可以使用左连接：

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')