如何避免 T-SQL 中的 "stringly typed" 代码？

Question

考虑一些代码，例如

SELECT
  CASE
    WHEN [DECISION-MAKER] = 'COKE' THEN 'GIVE COKE'
    WHEN [DECISION-MAKER] IN ('PEPSI', 'BLOOD') THEN 'GIVE DEATH'
  END AS [EMPLOYEE-ASSIGNMENT],
  CASE [DECISION-MAKER]
    WHEN 'COKE' THEN 'Employee prefers coke. Give coke.'
    WHEN 'PEPSI' THEN 'Employee prefers pepsi. Give death.'
    WHEN 'BLOOD' THEN 'Employee is some sort of vampire. Give death.'
   END AS [ASSIGNMENT-REASON]
FROM
  (
    SELECT *,
    CASE
      WHEN [COMPLEX-LOGIC-1] THEN 'COKE'
      WHEN [COMPLEX-LOGIC-2] THEN 'PEPSI'
      WHEN [COMPLEX-LOGIC-3] THEN 'BLOOD'
    END AS [DECISION-MAKER]
    FROM [WHEREVER]
  )

我相信这种糟糕代码的技术术语是“字符串类型”。上述代码中的关键问题是，决策是基于开发人员需要键入并始终正确的字符串输出做出的。如果出现任何问题，该语言将无法抛出错误。在传统语言中，解决方法是构建某种字典来处理这些情况。 T-SQL 中的惯用解决方案是什么？我不喜欢一次性 table 的想法，但也许临时 table 会有帮助？

Answer 1

uses "with as(query)"

with firstLogic as
(
   select PersonID, Name, 
   CASE
      WHEN valueDRINK=1 or valueDRINK=2 THEN 'COKE'
      WHEN valueDRINK=3 or valueDRINK=4 THEN 'PEPSI'
      WHEN valueDRINK=5 THEN 'BLOOD'
    END AS [DECISION-MAKER]
   from Persons
   where country='co'
)
select PersonID, Name ,[DECISION-MAKER],
  CASE
    WHEN [DECISION-MAKER] = 'COKE' THEN 'GIVE COKE'
    WHEN [DECISION-MAKER] IN ('PEPSI', 'BLOOD') THEN 'GIVE DEATH'
  END AS [EMPLOYEE-ASSIGNMENT],
  CASE [DECISION-MAKER]
    WHEN 'COKE' THEN 'Employee prefers coke. Give coke.'
    WHEN 'PEPSI' THEN 'Employee prefers pepsi. Give death.'
    WHEN 'BLOOD' THEN 'Employee is some sort of vampire. Give death.'
   END AS [ASSIGNMENT-REASON]
from firstLogic

“with”允许您进行不同的查询，然后在不创建临时查询的情况下加入它们 table

you can see it in this example

Answer 2

我不担心“在一个地方使用”table。如果您仍然担心它会弄乱您的数据库，您可以使用 table 变量。

DECLARE @AssignmentAndReason AS TABLE ( 
    DECISION-MAKER varchar, 
    EMPLOYEE-ASSIGNMENT varchar, 
    ASSIGNMENT-REASON varchar 
);

INSERT INTO @AssignmentAndReason VALUES
    ('COKE', 'GIVE COKE', 'Employee prefers coke. Give coke.'),
    ('PEPSI', 'GIVE DEATH', 'Employee prefers pepsi. Give death.'),
    ('BLOOD', 'GIVE DEATH', 'Employee is some sort of vampire. Give death.');

SELECT [EMPLOYEE-ASSIGNMENT], [ASSIGNMENT-REASON],
FROM [WHEREVER]
JOIN @AssignmentAndReason ON [DECISION-MAKER] = CASE
  WHEN [COMPLEX-LOGIC-1] THEN 'COKE'
  WHEN [COMPLEX-LOGIC-2] THEN 'PEPSI'
  WHEN [COMPLEX-LOGIC-3] THEN 'BLOOD'
END

如何避免 T-SQL 中的 "stringly typed" 代码？

How can I avoid "stringly typed" code in T-SQL?

sql

tsql

sql-server

string

dictionary