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MS SQL join, include all in table 1 and show null when table 2..

Posted on 2013-01-07
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Last Modified: 2013-01-07
MS SQL to include all users and include null when no assigned taskdetail and value when there is a task detail. See below;

Users
User_ID   name
1               Joe
2               Mary
3               James
4               Mathew
5               Sam


TaskDetail
TaskDetail_ID  FK_User_ID  FK_TaskName_ID

1                          1            2
2                          4            1
3                          3            2
4                          1            3
5                            1                1
6                            1                5

I want to have all users returned for a specific task whether they are assigned to it or not.

Result for when FK_TaskName_ID = 2 should result as follows

Name             FK_User_ID        FK_TaskName_ID
Joe                          1                  2
Mary                  2                  null
James                  3                  2
Mathew                  4                  null                  
Sam                          5                  null
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Question by:petel2k
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7 Comments
 
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Expert Comment

by:Jim Horn
ID: 38751038
Two things:

(1)  That would be a LEFT JOIN, which means 'return all rows in the table LEFT of the join, and include only values from the right of the LEFT join where they exist.

(2)  >I want to have all users returned for a specific task...
The below CASE block handles that, although I'm sure you'll want to change the hard-coded 2 to include a @variable, or however you're determining the FK_TaskName_ID value.

SELECT users.Name, TaskDetail.FK_User_ID, CASE WHEN TaskDetail.FK_TaskName_ID = 2 THEN 2 ELSE NULL END as FK_TaskName_ID
FROM users
LEFT JOIN TaskDetail ON users.user_id = TaskDetail.FK_USER_ID
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Author Comment

by:petel2k
ID: 38751082
error
Msg 102, Level 15, State 1, Line 3
Incorrect syntax near '.'.

'FROM users'
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LVL 65

Expert Comment

by:Jim Horn
ID: 38751144
Check the spelling of all table and column names to make sure they match.
The T-SQL I posted looks correct as far as syntax.
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Accepted Solution

by:
sachitjain earned 500 total points
ID: 38751148
select U.Name, T.FK_User_Id, T.FK_TaskName_ID
from Users U left join TaskDetail T on U.UserId = T.FK_User_Id and T.FK_TaskName_ID = 2
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Author Closing Comment

by:petel2k
ID: 38751173
Great job!!! Thanks for the help
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Expert Comment

by:Jim Horn
ID: 38751369
How's that answer different from the one I posted earlier?  Just curious.
The CASE block does the same as the WHERE.
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Author Comment

by:petel2k
ID: 38751384
Hey Jim..

In your case, your also worked. And I misspelled. Both solutions worked. I need to modify award as a split. Sorry.
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