ORA-00905缺失关键字报错：请帮忙修正指定SQL语句错误

原执行报错的SQL语句：

select employee_id,case first_name when first_name = "Steve" then "My name is Steve" 
                        else first_name
end
from hr.employees
where 
employee_id = 150;

修正后的正确SQL语句 #

写法一：匹配值形式的CASE表达式

select employee_id,
       case first_name 
           when 'Steve' then 'My name is Steve' 
           else first_name
       end
from hr.employees
where employee_id = 150;

写法二：条件判断形式的CASE表达式

select employee_id,
       case 
           when first_name = 'Steve' then 'My name is Steve' 
           else first_name
       end
from hr.employees
where employee_id = 150;

错误原因 #

• 使用case first_name when语法时，when后应直接跟匹配值，不能写first_name = "Steve"这类条件表达式
• Oracle中字符串常量必须用单引号包裹，双引号仅用于标识符（比如特殊命名的列名、表名）

内容的提问来源于stack exchange，提问作者Saketh Patchava