尝试查找特定值时，SQL查询返回多行

Question

I have 2 tables. One is called "Tasks" and the other one is called "TaskDescription" in my "Task" the setup looks like this: "taskID(primary)","FileID","TaskTypeID" and a bunch of other columns irrelevant.

Then in my "TaskDescription", the setup looks like: "TaskTypeID", "TaskTypeDesc"

so for example if TaskTypeID is 1 , then the description would be"admin" or if TaskTypeID is 2, then TaskTypeDesc would be "Employee" etc.

The two tables have a relationship on the primary/foreign key "TaskTypeID".

What I am trying to do is get a task id, and the TaskDesc where the FileID matches the @fileID(which I pass in as a param). However in my query I get multiple rows returned instead of a single row when trying to obtain the description.

this is my query:

SELECT taskid,
       ( 'Task ID: '
         + Cast(cf.taskid AS NVARCHAR(15)) + ' - '
         + Cast((SELECT DISTINCT td.tasktypedesc FROM casefiletaskdescriptions
         td JOIN
         casefiletasks cft ON td.tasktypeid=cft.tasktypeid WHERE cft.taskid =
         1841 )AS
         NVARCHAR(100))
         + ' - Investigator : ' + ( Cast(i.fname AS NVARCHAR(20)) + ' '
                                    + Cast(i.lname AS NVARCHAR(20)) ) ) AS
       'Display'
FROM   casefiletasks [cf]
       JOIN investigators i
         ON CF.taskasgnto = i.investigatorid
WHERE  cf.fileid = 2011630988
       AND cf.concluded = 0
       AND cf.progressflag != 'Conclude' 

I am trying to get the output to look like "Task ID: 1234 - Admin - Investigator : John Doe". However I am having trouble on this part:

CAST((select DISTINCT td.TaskTypeDesc from CaseFileTaskDescriptions td 
JOIN CaseFileTasks cft ON td.TaskTypeID=cft.TaskTypeID 
where cft.TaskID =1841 )as nvarchar(100))

This seems to work but the problem is I have to hard code the value "1841" to make it work. Is there a way to assign a "taskID" variable with the values being returned from the TaskID select query, or will it not work since I think sql runs everything at once instead of line by line.

EDIT-this is in Microsoft SQL Server Management Studio 2008

Answer 1

You can dynamically reference a column that exists in your FROM set. In this case, it would be any column from casefiletasks or investigators . You would replace 1841 with the table.column reference.

Update

Replacing your static integer with the column reference, your query would look like:

SELECT taskid,
       ( 'Task ID: '
         + Cast(cf.taskid AS NVARCHAR(15)) + ' - '
         + Cast((SELECT DISTINCT td.tasktypedesc FROM casefiletaskdescriptions
         td JOIN
         casefiletasks cft ON td.tasktypeid=cft.tasktypeid WHERE cft.taskid =
         cf.taskid )AS
         NVARCHAR(100))
         + ' - Investigator : ' + ( Cast(i.fname AS NVARCHAR(20)) + ' '
                                    + Cast(i.lname AS NVARCHAR(20)) ) ) AS
       'Display'
FROM   casefiletasks [cf]
       JOIN investigators i
         ON CF.taskasgnto = i.investigatorid
WHERE  cf.fileid = 2011630988
       AND cf.concluded = 0
       AND cf.progressflag != 'Conclude' 

Answer 2

Would this work as your inner query?

SELECT DISTINCT td.TaskTypeDesc FROM CaseFileTaskDescriptions td 
JOIN CaseFileTasks cft ON td.TaskTypeID = cft.TaskTypeID 
WHERE cft.TaskID = cf.TaskID

Answer 3

Why not just do another join instead of a subquery?

SELECT taskid,
       ( 'Task ID: '
         + Cast(cf.taskid AS NVARCHAR(15)) + ' - '
         + Cast(td.tasktypedesc AS NVARCHAR(100))
         + ' - Investigator : ' + ( Cast(i.fname AS NVARCHAR(20)) + ' '
                                    + Cast(i.lname AS NVARCHAR(20)) ) ) AS
       'Display'
FROM   casefiletasks [cf]
       JOIN investigators i
         ON CF.taskasgnto = i.investigatorid
       JOIN casefiletaskdescriptions td
         ON td.tasktypeid = cf.tasktypeid
WHERE  cf.fileid = 2011630988
       AND cf.concluded = 0
       AND cf.progressflag != 'Conclude'