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You can find a lot of debugging and deploying problems while developing applications in .NET and Visual Basic here. There are also some querying tips in SQL and typical source codes which might be useful shared here.

Report cannot be Displayed

Error:
- Event not fired.
- Microsoft.Reporting.WebForms.HttpHandlerInputException: Missing URL parameter: IterationId
(This is only part of the long error message).
- Report loads forever (never stops loading).

Solution:
On the aspx page, add attribute: EnableEventValidation="false"

For my particular case, I was trying to display a report (SSRS), and it never stopped loading. However, for my case, it was because of the version of the Internet Explorer (yes, the report is only compatible with IE for mine). After changing the version of the IE through developer tool (F12), I managed to display the report properly. You can also try to display the report from another machine using the intended IE version to see if it displays properly.
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Combine Rows into a Column

Happened to find a way to combine rows into a column. I find it quite useful, and it comes in handy.

For illustration, suppose we have UserGroup & Users. We want to list the users belonging to each group.

UserGroup:


Users:


If we do normal joining of the 2 tables, it will look like:


If we combine the values on the rows into a column, it will look like:


Here is the query to do so:

-- Create temporary table to store UserGroup
SELECT GroupID = 1, UserGroup = 'Group 1' INTO #UserGroup
INSERT INTO #UserGroup VALUES ( 2, 'Group 2' )
INSERT INTO #UserGroup VALUES ( 3, 'Group 3' )

-- Create temporary table to store Users
SELECT UserID = 'Superman', GroupID = 1 INTO #Users
INSERT INTO #Users VALUES ( 'Luck', 2 )
INSERT INTO #Users VALUES ( 'Himura', 1 )
INSERT INTO #Users VALUES ( 'Selvi', 1 )
INSERT INTO #Users VALUES ( 'Smarty', 2 )
INSERT INTO #Users VALUES ( 'Lucky', 3 )

-- Normal Join
SELECT a.UserGroup, b.UserID
FROM #UserGroup a
LEFT JOIN #Users b
 ON b.GroupID = a.GroupID
ORDER BY a.UserGroup

-- Combine Rows into Column
SELECT UserGroup, Users = STUFF(( SELECT ', ' + UserID FROM #Users a
    WHERE a.GroupID = b.GroupID
    ORDER BY a.UserID
    FOR XML PATH('') )
   , 1, 2, '')
FROM #UserGroup b
ORDER BY UserGroup

-- This is the key query to combine rows into column
SELECT UserID + ', ' FROM #Users
WHERE GroupID = 1
FOR XML PATH('')
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Mapping User Login and Database Roles to Existing User

Error:
User, group, or role 'xxx' already exists in the current database. (.Net SqlClient Data Provider)

Explanation:
This error happens when you try to add user mapping to the server logins using username which already exists in the database to be assigned.

In my case, the user exists in both server logins and database logins, but the user mapping and database roles on the server logins for this user cannot be modified although the user mapping is incorrect, because it already exists on the database logins.

Solution:
Run this script to update the user mapping accordingly.
USE <database_name>
EXEC sp_change_Users_login 'update_one', '<login_username>', '<login_username>'

This will update the user mapping and database roles on server logins to follow the ones on the database logins.
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Current Transaction Cannot be Committed

Error:
The current transaction cannot be committed and cannot support operations that write to the log file. Roll back the transaction.

This error occurs when you try to perform other operations when any transaction fails in try catch section, soon after it goes to catch section.

Solution:
You have to ROLLBACK first on the catch section before doing any other operations.
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Directory Lookup Failed on SQL Server

When executing script on SQL server, this error occurs:
Directory lookup for the file <filepath> failed with the operating system error 2(The system cannot find the file specified.)

Directory lookup for the file <filepath> failed with the operating system error 3(The system cannot find the path specified.)

Solution:
Check the directory used in the SQL script. Make sure that the directory used in the SQL script point to the server location, if the script is not directly executed from the server.
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