Sql server 使用带有SQL游标的case语句对每行执行计算并对结果求和

我使用case语句和游标对每一行执行计算，然后显示结果的总和

我有一张这样的桌子：

ID  Name    Amount  Income_Frequency
123 Sam     500     Bi-weekly
123 Ralf    200     Weekly
123 Floyd   10000   Annual

我需要对每行执行如下计算：

SELECT
    CASE
        WHEN Income_Frequency = 'Weekly' THEN Amount * 52
        WHEN Income_Frequency = 'Bi-weekly' THEN Amount * 26
        WHEN Income_Frequency = 'Monthly' THEN Amount * 12
        WHEN Income_Frequency = 'Annual' THEN Amount * 1
    ELSE '0'
    END
    

山姆的总收入应该是13000，拉尔夫10400，弗洛伊德10000。然后我需要将这3个金额相加，得到33400

以下是我尝试过但不起作用的方法：

DECLARE @Total decimal(9,2)

DECLARE MY_CURSOR CURSOR 
  LOCAL STATIC READ_ONLY FORWARD_ONLY
FOR 
(SELECT TOP(1)
        CASE
            WHEN Income_Frequency = 'Weekly' THEN Amount * 52
            WHEN Income_Frequency = 'Bi-weekly' THEN Amount * 26
            WHEN Income_Frequency = 'Monthly' THEN Amount * 12
            WHEN Income_Frequency = 'Annual' THEN Amount * 1
        ELSE '0'
        END  as AnnualIncome
        FROM MyTable where ID = 123)

OPEN MY_CURSOR
FETCH NEXT FROM MY_CURSOR INTO @Total
WHILE @@FETCH_STATUS = 0
BEGIN 
    FETCH NEXT FROM MY_CURSOR INTO @Total
    SELECT SUM(@Total)
END
CLOSE MY_CURSOR
DEALLOCATE MY_CURSOR

---

只是想进一步阐述一下史蒂夫的评论

示例或

结果

Annual
33400

试试这个：

MS SQL Server 2017架构设置：

CREATE TABLE MyTable
(
  ID      INT,
  Name    VARCHAR(20),
  Amount  Decimal(9,2),
  Income_Frequency VARCHAR(20)
)

INSERT INTO MyTable
VALUES
  (123,  'Sam',500, 'Bi-weekly'),
  (123,  'Ralf',200, 'Weekly'),
  (123,  'Floyd',10000, 'Annual') 

DECLARE @Total decimal(9,2)

SELECT @Total= SUM(
        CASE
            WHEN Income_Frequency = 'Weekly' THEN Amount * 52
            WHEN Income_Frequency = 'Bi-weekly' THEN Amount * 26
            WHEN Income_Frequency = 'Monthly' THEN Amount * 12
            WHEN Income_Frequency = 'Annual' THEN Amount * 1
            ELSE 0
        END)  
FROM MyTable
where ID = 123

SELECT @Total

|       |
|-------|
| 33400 |

查询1：

CREATE TABLE MyTable
(
  ID      INT,
  Name    VARCHAR(20),
  Amount  Decimal(9,2),
  Income_Frequency VARCHAR(20)
)

INSERT INTO MyTable
VALUES
  (123,  'Sam',500, 'Bi-weekly'),
  (123,  'Ralf',200, 'Weekly'),
  (123,  'Floyd',10000, 'Annual') 

DECLARE @Total decimal(9,2)

SELECT @Total= SUM(
        CASE
            WHEN Income_Frequency = 'Weekly' THEN Amount * 52
            WHEN Income_Frequency = 'Bi-weekly' THEN Amount * 26
            WHEN Income_Frequency = 'Monthly' THEN Amount * 12
            WHEN Income_Frequency = 'Annual' THEN Amount * 1
            ELSE 0
        END)  
FROM MyTable
where ID = 123

SELECT @Total

|       |
|-------|
| 33400 |

：

CREATE TABLE MyTable
(
  ID      INT,
  Name    VARCHAR(20),
  Amount  Decimal(9,2),
  Income_Frequency VARCHAR(20)
)

INSERT INTO MyTable
VALUES
  (123,  'Sam',500, 'Bi-weekly'),
  (123,  'Ralf',200, 'Weekly'),
  (123,  'Floyd',10000, 'Annual') 

DECLARE @Total decimal(9,2)

SELECT @Total= SUM(
        CASE
            WHEN Income_Frequency = 'Weekly' THEN Amount * 52
            WHEN Income_Frequency = 'Bi-weekly' THEN Amount * 26
            WHEN Income_Frequency = 'Monthly' THEN Amount * 12
            WHEN Income_Frequency = 'Annual' THEN Amount * 1
            ELSE 0
        END)  
FROM MyTable
where ID = 123

SELECT @Total

|       |
|-------|
| 33400 |

---

为什么要使用游标，一个简单的查询和一个大小写就可以了fine@SteveFord我试过了，但总共得到了10000个。谢谢。只是要补充一点，很少有情况下你需要使用光标。尽量避免它们，因为它们没有表现出来，而且更难理解。SQL是一种基于集合的语言，应该以这种方式使用，而不是使用迭代。请注意，

CASE

可以写得稍微优雅一些（IMO），因为当“每周”时，

CASE-Income\u频率为52…

ELSE可以完全省略，而不会影响结果（但如果它仍然存在，它应该是

0

，而不是

'0'

）。只需在Steve的评论上展开展开即可。由于数学与当前行的值直接相关（简单数学）-SQL Server将能够执行“基于集合的操作”它将比游标更快、效率更高。如果您在游标循环中进行求和或平均值运算，则可能是做错了。@SqlSurfer您是对的。更多单词…更好：）跳过了@Total+1