sql - Oracle SQL - CASE 语法

Question

假设这个查询功能正常：

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;

为什么我不能使用一些布尔逻辑添加另一个 WHEN 子句，而不是上面两个 WHEN 子句中隐含的等于？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;

引发此错误：

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详细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

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
/

Answer 2

是的，你是对的，不幸的是，短语法中不可能有条件。

文档将短语法 称为“simple_case_expression”

CASE expr WHEN comparision_expr THEN return_expr