Compile error - Dynamic SQL - sql-server

Question

I've tried to implement some dynamic SQL to create a cursor as an extension of a simple SELECT query. The cursor is used as a way to print the GROUPED values returned from the SELECT as a message in SQL Server Management Studio (kind of like a visual summary of the data) . The purpose of this approach is half task related and half to benefit my understanding of how dynamic SQL can be developed. Code reads:
DECLARE #Focus VARCHAR(10);
SET #Focus = 'Completed'; /* User input event focus {Started, Completed} */
DECLARE #PeriodStartDate DATE, #PeriodEndDate DATE;
SET #PeriodStartDate = '04/01/2014';
SET #PeriodEndDate = GETDATE();
DECLARE #sql VARCHAR(MAX);
SET #sql =
'SELECT ' +
'CASE DATEPART(M, ' + '[Event ' + CASE #Focus
WHEN 'Started' THEN 'Start'
WHEN 'Completed' THEN 'End'
END + ' Date]) ' +
' WHEN 1 THEN ''January'' ' +
' WHEN 2 THEN ''February'' ' +
' WHEN 3 THEN ''March'' ' +
' WHEN 4 THEN ''April'' ' +
' WHEN 5 THEN ''May'' ' +
' WHEN 6 THEN ''June'' ' +
' WHEN 7 THEN ''July'' ' +
' WHEN 8 THEN ''August'' ' +
' WHEN 9 THEN ''September'' ' +
' WHEN 10 THEN ''October'' ' +
' WHEN 11 THEN ''November'' ' +
' WHEN 12 THEN ''December'' ' +
' END AS [Event ' + #Focus + ' Month], ' +
' COUNT([Unique ID]) AS [Number of Events] ' +
' FROM [udf_Events](' + #Focus + ', ' + CAST(#PeriodStartDate AS VARCHAR) + ', ' + CAST(#PeriodEndDate AS VARCHAR) + ') ' +
' GROUP BY ' +
' DATEPART(M, ' + '[Event ' + CASE #Focus
WHEN 'Started' THEN 'Start'
WHEN 'Completed' THEN 'End'
END + ' Date]) ' +
' ORDER BY ' +
' DATEPART(M, ' + '[Event ' + CASE #Focus
WHEN 'Started' THEN 'Start'
WHEN 'Completed' THEN 'End'
END + ' Date]) '
;
DECLARE Results CURSOR
FOR
SELECT
#sql;
The error message I receive:
Msg 16924, Level 16, State 1, Line 71 Cursorfetch: The number of
variables declared in the INTO list must match that of selected
columns.
Through grappling with the problem and trying to execute the query as a SELECT statement (removing the complexity of the cursor) using EXEC(#sql) the error message reads:
Invalid column name 'Completed'.
..Which leads me to believe the problem lies with the CASE expression in the first field selected. udf_Events is an in-line table valued function with three arguments. Amongst others, it has columns [Event Start Date] and [Event End Date] which are the values the cursor is looking to do its work on.

Answer 1

Try this...few ' were missing in your query
DECLARE #Focus VARCHAR(10);
SET #Focus = 'Completed'; /* User input event focus {Started, Completed} */
DECLARE #temp VARCHAR(500);
IF(#Focus = 'Completed')
SET #temp = '[Event End Date]'
ELSE
SET #temp = '[Event Start Date]'
DECLARE #PeriodStartDate DATE, #PeriodEndDate DATE;
SET #PeriodStartDate = '04/01/2014';
SET #PeriodEndDate = GETDATE();
DECLARE #sql VARCHAR(MAX);
SET #sql =
'SELECT ' +
'CASE DATEPART(M, ' + #temp + ')' +
' WHEN 1 THEN ''January'' ' +
' WHEN 2 THEN ''February'' ' +
' WHEN 3 THEN ''March'' ' +
' WHEN 4 THEN ''April'' ' +
' WHEN 5 THEN ''May'' ' +
' WHEN 6 THEN ''June'' ' +
' WHEN 7 THEN ''July'' ' +
' WHEN 8 THEN ''August'' ' +
' WHEN 9 THEN ''September'' ' +
' WHEN 10 THEN ''October'' ' +
' WHEN 11 THEN ''November'' ' +
' WHEN 12 THEN ''December'' ' +
' END AS [Event ' + #Focus + ' Month], ' +
' COUNT([Unique ID]) AS [Number of Events] ' +
' FROM [udf_Events](''' + #Focus + ''', ''' + CAST(#PeriodStartDate AS VARCHAR) + ''', ''' + CAST(#PeriodEndDate AS VARCHAR) + ''') ' +
' GROUP BY ' +
' DATEPART(M, ' + #temp + ')' +
' ORDER BY ' +
' DATEPART(M, ' + #temp + ')';
print #sql

Answer 2

You're not quoting the dates in the call to udf_Events so you end up with
[udf_Events](Completed, 2014-04-01, 2014-09-19)
instead of
[udf_Events](Completed, '2014-04-01', '2014-09-19')
The fix is to change the line
' FROM [udf_Events](' + #Focus + ', ' + CAST(#PeriodStartDate AS VARCHAR) + ', ' + CAST(#PeriodEndDate AS VARCHAR) + ') ' +
to
' FROM [udf_Events](' + #Focus + ', ''' + CAST(#PeriodStartDate AS VARCHAR) + ''', ''' + CAST(#PeriodEndDate AS VARCHAR) + ''') ' +
That said, if the parameters to udf_Events are datetimes then I would consider changing the format to YYYYMMDD as this is unambiguous. To do this you can use CONVERT(char(8), <date>, 112) where <date> is the date to be converted.
i.e:
' FROM [udf_Events](' + #Focus + ', ''' + CONVERT(char(8), #PeriodStartDate, 112) + ''', ''' + CONVERT(char(8), #PeriodEndDate, 112) + ''') ' +