这是一个演示查询，请注意，这非常简单，仅在base_price为0的地方获取，并且仍然选择条件3：

SELECT
   CASE course_enrollment_settings.base_price
    WHEN course_enrollment_settings.base_price = 0      THEN 1
    WHEN course_enrollment_settings.base_price<101      THEN 2
    WHEN course_enrollment_settings.base_price>100 AND   
                      course_enrollment_settings.base_price<201 THEN 3
        ELSE 6
   END AS 'calc_base_price',
   course_enrollment_settings.base_price
FROM
    course_enrollment_settings
WHERE course_enrollment_settings.base_price = 0

base_price 是 decimal(8,0)

在数据库上运行此命令时，我得到：

3 0
3 0
3 0
3 0
3 0