Oracle SQL - CASE 语法

Question

假设这个查询运行良好：

SELECT 
   first_name,
   consultant_id,
   CASE consultant_id
    WHEN 1 THEN 'First Consultant'
    WHEN 2 THEN 'Second Consultant'
   END
FROM consultant
ORDER BY first_name;

除了上面两个 WHEN 子句中隐含的等于之外，为什么我不能使用布尔逻辑添加另一个 WHEN 子句？例如：

SELECT 
   first_name,
   consultant_id,
   CASE consultant_id
    WHEN 1 THEN 'First Consultant'
    WHEN 2 THEN 'Second Consultant'
    WHEN BETWEEN 3 AND 12 THEN 'Everyone else'
   END
FROM consultant
ORDER BY first_name;

抛出此错误：

ORA-00936: missing expression
00936. 00000 -  "missing expression"
*Cause:    
*Action:
Error at Line: 7 Column: 10

有没有办法在不使用更冗长的情况下完成这项工作：

SELECT 
   first_name,
   consultant_id,
   CASE 
    WHEN consultant_id = 1 THEN 'First Consultant'
    WHEN consultant_id = 2 THEN 'Second Consultant'
    WHEN consultant_id BETWEEN 3 AND 12 THEN 'Everyone else'
   END
FROM consultant
ORDER BY first_name;

Answer 1

是的，你是对的，很遗憾，短语法中不可能有条件。

documentation 调用短语法 "simple_case_expression"

CASE expr WHEN comparision_expr THEN return_expr

Answer 2

此外，根据您的要求，您可以使用：

SELECT
   first_name,
   consultant_id,
   CASE consultant_id
    WHEN 1 THEN 'First Consultant'
    WHEN 2 THEN 'Second Consultant'
    ELSE 'Everyone else'
   END
FROM consultant
ORDER BY first_name
/

Oracle SQL - CASE 语法

Oracle SQL - CASE syntax

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oracle

case-when

booleanquery