MySQL查询选择值在日期范围内的所有行

我有以下MySQL查询：

SELECT 
  s.student_socialnr, s.student_lastname, s.student_firstname,
  cs.city_name,
  scp.cpl_startdate, scp.cpl_enddate, scp.cpl_invoice,
  cu.customer_name, scp.cpl_coursename
FROM students s
 INNER JOIN studentcourseplan scp ON scp.student_id = s.student_id
 INNER JOIN cityselections cs ON cs.city_id = s.student_city_id
 INNER JOIN customers cu ON cu.customer_id = s.student_customer_id

这将输出如下内容：

+------------------+------------------+------------------+-----------+---------------+--------------+-------------+---------------+----------------+
| student_socialnr | student_lastname | student_firstname| city_name | cpl_startdate | cpl_enddate  | cpl_invoice | customer_name | cpl_coursename |
+------------------+------------------+------------------+-----------+---------------+--------------+-------------+---------------+----------------+
| 000000-0000      | Doe              | John             | Dallas    | 2012-06-01    | 2012-06-30   | 1337        | The customer  | The course     |
+------------------+------------------+------------------+-----------+---------------+--------------+-------------+---------------+----------------+
| 000000-0000      | Johnsson         | Derp             | Texas     | 2012-02-01    | 2012-07-28   | 5000        | The customer  | The course     |
+------------------+------------------+------------------+-----------+---------------+--------------+-------------+---------------+----------------+
| 000000-0000      | Derpina          | Lisa             | New York  | 2013-01-01    | 2013-04-01   | 2001        | The customer  | The course     |
+------------------+------------------+------------------+-----------+---------------+--------------+-------------+---------------+----------------+

我没有两个问题。我希望能够在

cpl\u startdate

和

cpl\u enddate

字段上设置过滤器。因此，例如，如果用户设置过滤器

cpl_startdate='2012-01-01'

和

cpl_enddate='2012-12-31'

，则应输出日期在该范围内的所有行。因此，使用上面的示例，它应该只输出前两行，因为它们在选定的日期范围内

我试过了

.. WHERE scp.cpl_startdate <= '2012-01-01' AND scp.cpl_enddate >= '2012-12-31'

。。其中scp.cpl_startdate='2012-12-31'

。。没有运气。我可以在之间使用MySQL语法吗？

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另外，是否可以计算两个日期范围之间的天数？我想输出跨度之间天数的整数。不一定在同一查询中。

切换比较符号：

.. WHERE scp.cpl_startdate >= '2012-01-01' AND scp.cpl_enddate <= '2012-12-31'

DATEDIFF（expr1，expr2）返回expr1-expr2之间的日期差。请参阅MySQL中的更多内容

DATEDIFF(scp.cpl_enddate, scp.cpl_startdate) AS DaysDifference