Question

在SQL Server中，我不能多次引用WITH表达式？

DECLARE @total FLOAT;

WITH cte AS (
  SELECT s.plate, SUM(s.net) AS tonnage
    FROM scale s
    GROUP BY s.plate
)
SELECT @total = SUM(tonnage) / 100 FROM cte;
SELECT t.*, t.tonnage / @total AS percentage FROM cte t;

Answer 1

来自MSDN WITH common_table_expression (Transact-SQL)

这是从一个简单的查询派生而来，并在执行中定义单个 SELECT，INSERT，UPDATE或DELETE语句的范围。

CTE是表达式，将在执行第一个语句后处理，并且在

之后将不可用

在您的情况下，您必须两次查询Scale表以计算总和

DECLARE @Total DECIMAL(19,4) = (SELECT SUM(Net)/100.0 FROM Scales)

SELECT s.PlateID
, SUM(s.Net) AS Tonnage
, SUM(s.Net)/@Total AS Percentage
FROM Scales s
GROUP BY s.PlateID

Answer 2

来自MSDN

公用表表达式（CTE）可以被认为是临时表在单个执行范围内定义的结果集 SELECT，INSERT，UPDATE，DELETE或CREATE VIEW语句。 CTE是类似于派生表，因为它不存储为对象和仅持续查询的持续时间。

所以你可以尝试这样的事情，但你在查询中缺少Group by

WITH cte
     AS (SELECT s.plate,
                Sum(s.net) AS tonnage
         FROM   scale s
         GROUP  BY s.plate)
SELECT t.plate,
       t.tonnage / ( Sum(tonnage) / 100.0 ) AS percentage,
       Sum(tonnage) / 100.0                 AS total
FROM   cte t
Group by plate

Answer 3

因为 CTE 的执行范围是针对单个SELECT，INSERT，UPDATE或DELETE语句。我想你应该为此而努力......

WITH cte AS (
  SELECT s.plate, SUM(s.net) AS tonnage
    FROM scale s
    GROUP BY s.plate
)
SELECT t.*,
       t.tonnage / ( Sum(tonnage) / 100.0 ) AS percentage
FROM   cte t;

为什么我不能多次引用WITH表达式？

3 个答案: