如何在不输入两次公式的情况下将负结果设置为零

Question

我知道如何将负值设置为零：

select case when (formula) < 0 then 0 else (formula) end as result from tab

但是如果“公式”是一个很长的公式呢？然后我必须输入两次。有没有一种方法可以在不输入两次公式的情况下获得相同的结果？

我的实际情况是这样的：

select
  sum
  ( 
      case when 
      (t1.x + t2.x + t3.x) * t4.p - (t5.x + t6.x + t7.x) * t8.p ) < 0
      then 0 
      else 
      (t1.x + t2.x + t3.x) * t4.p - (t5.x + t6.x + t7.x) * t8.p )
      end
  ) as result
from 
     t1 
     left join t2 on t1.x = t2.x 
     left join t3 on t1.x = t3.x 
     ... etc ....

t2、t3、t4 等来自为某些账户提供价值的 cte 报表。

Answer 1

您可以尝试以下方法：

VALUES table 值构造函数和 MAX 聚合函数。
APPLY 运算符和 MAX 聚合函数。

T-SQL:

SELECT (SELECT MAX(result) FROM (VALUES (0), (tab.x)) v(result)) AS result
FROM (VALUES
   (2 - 3),
   (4 + 5)
) tab (x)

SELECT apl.result
FROM (VALUES
   (2 - 3),
   (4 + 5)
) tab (x)
CROSS APPLY (SELECT MAX(x) FROM (VALUES (0), (tab.x)) v (x)) apl (result)

以下示例基于问题中的代码，是一个可能的解决方案：

SELECT x INTO t1 FROM (VALUES (-1), (1)) v (x)
SELECT x INTO t2 FROM (VALUES (-1), (1)) v (x)
SELECT x INTO t3 FROM (VALUES (-1), (1)) v (x)

SELECT SUM(a.result)
FROM t1 
LEFT JOIN t2 ON t1.x = t2.x 
LEFT JOIN t3 ON t1.x = t3.x
CROSS APPLY (
   SELECT MAX(x) FROM (VALUES (0), (t1.x + t2.x + t3.x)) v (x)
) a (result)

Answer 2

使用CTE.

DECLARE @Table1 TABLE
(
    ID INT,
    A INT,
    B INT
);

DECLARE @Table2 TABLE
(
    ID INT,
    C INT,
    D INT
);

INSERT @Table1 VALUES
    ( 1,  1,  2),
    ( 2,  3, -4),
    ( 3, -5, -6);

INSERT @Table2 VALUES
    ( 1, -7,  8),
    ( 2,  9, 10),
    ( 3, 11, 12);
    
WITH query (Formula)
AS
(
    SELECT (A + B) * (C - D) AS Formula
        FROM @Table1 T1 INNER JOIN @Table2 T2 ON T1.ID = T2.ID
)
SELECT Formula, CASE WHEN Formula < 0 THEN 0 ELSE Formula END AS Result
    FROM query

结果：

Answer 3

这可以使用一个简单的子查询来完成，例如

select
    sum
    ( 
        case when ForumulaResult < 0
        then 0 
        else ForumulaResult
        end
    ) as result
from (
    select
        (t1.x + t2.x + t3.x) * t4.p - (t5.x + t6.x + t7.x) * t8.p) as ForumulaResult
    from t1 
    left join t2 on t1.x = t2.x 
    left join t3 on t1.x = t3.x 
    -- ... etc ....
) x;

或使用cross apply

select
    sum
    ( 
        case when ForumulaResult < 0
        then 0 
        else ForumulaResult
        end
    ) as result
from t1 
left join t2 on t1.x = t2.x 
left join t3 on t1.x = t3.x 
cross apply (select (t1.x + t2.x + t3.x) * t4.p - (t5.x + t6.x + t7.x) * t8.p ) as ForumulaResult) x

或者使用已显示的 CTE...尽管您表示您已经有一个 CTE 生成起始数据...因此可能更难合并。

从表面上看，@Han提供的简单数据，它们都产生了相同的执行计划，所以真正使用到哪个的选择对你来说更清楚。

如何在不输入两次公式的情况下将负结果设置为零

How to set a negative result to zero without typing the formula twice

sql

tsql

sql-server

sql-server-2014