不确定是什么导致了 sql 错误 306

Question

我原来在sql上有如下查询：

SELECT PROJECT_TYPE.PROJECT_TYPE_NAME, PROJECT.PROJECT_NAME, STATUS_TYPE.STATUS_TYPE_NAME,
COUNT(*) AS Tasks
FROM TASK
INNER JOIN PROJECT ON PROJECT.PROJECT_ID = TASK.PROJECT_ID
AND PROJECT.POURCENTAGE < 100               /* the following ANDs filters out inactive projects */
AND PROJECT.PROJECT_TYPE < 6
AND PROJECT.PROJECT_STATUS_ID < 3
INNER JOIN PROJECT_TYPE ON PROJECT.PROJECT_TYPE = PROJECT_TYPE.PROJECT_TYPE_ID
INNER JOIN STATUS_TYPE ON TASK.STATUS_TYPE_ID = STATUS_TYPE.STATUS_TYPE_ID
INNER JOIN PRIORITY_TYPE ON TASK.PRIORITY_TYPE_ID = PRIORITY_TYPE.PRIORITY_TYPE_ID
AND NOT PRIORITY_TYPE.PRIORITY_TYPE_NAME = 'Hold'                           
AND STATUS_TYPE.STATUS_TYPE_NAME IN ('To do','In Progress', 'To Verify')        /* only include projects in these 3 statuses */
GROUP BY PROJECT_TYPE.PROJECT_TYPE_NAME, PROJECT.PROJECT_NAME, STATUS_TYPE.STATUS_TYPE_NAME
order by 2, case status_type_name   /* orders by status */
  when 'To do' then 1
  when 'In Progress' then 2
  when 'To Verify' then 3
  else 4
  end

它正确地将特定状态下的任务数显示为such。但是，我想替换

project.project_name

在另一个名为

的表中列出了较短描述的表

project.project_desc

，看起来像this。我尝试通过将所有 project.project_name 替换为 project.project_desc 并添加

来实现这一点

AND PROJECT.PROJECT_DESC IS NOT NULL

第一个inner join下。但是，这会导致以下错误

SQL 错误 (306)：text、ntext 和 image 数据类型不能 比较或排序，除非使用 IS NULL 或 LIKE 运算符。

我现在不确定这有什么问题，所有的空值都应该被过滤掉，所以我很困惑为什么查询不像以前那样运行，只是读取不同的表.我无权编辑数据库，所以这些更改必须通过查询来实现。

Answer 1

FWIW，我觉得这更容易阅读......

SELECT pt.project_type_name
     , p.project_name
     , st.status_type_name
     , COUNT(*) tasks
  FROM task t
  JOIN project p  
    ON p.project_id = t.project_id
  JOIN project_type pt
    ON pt.project_type_id = p.project_type 
  JOIN status_type st
    ON st.status_type_id = t.status_type_id 
  JOIN priority_type xt
    ON xt.priority_type_id = task.priority_type_id 
 WHERE p.pourcentage < 100               
   AND p.project_type < 6
   AND p.project_status_id < 3
   AND xt.priority_type_name != 'hold'                           
   AND st.status_type_name IN('to do','in progress', 'to verify')  
 GROUP 
    BY pt.project_type_name
     , p.project_name
     , st.status_type_name
 ORDER 
    BY p.project_name
     , FIELD(status_type_name,'to do','in progress','to verify')