Declare Scalar variable - sql

Question

I am writing a dynamic SQL statement that is failing with the error
Must declare the scalar variable "##config"
I have tried to break the code down and can confirm that the following code does return results:
Declare ##sql as nvarchar(max);
Declare #SourceDatabase as nvarchar(10);
Declare #DestDatabase as nvarchar(10);
Declare ##Harray as nvarchar(max) ;
Set #SourceDatabase = 'D_EXP_CPM';
Set #DestDatabase = 'T_EXP_CPM';
set ##sql = 'SELECT B.Hierarchy_SKey AS ''NEW'', A.Hierarchy_SKey AS ''OLD''
INTO ##TEMPHCONVERT
FROM ' + #SourceDatabase + '.[dbo].[DIM_HIERARCHY] A
INNER JOIN ' + #DestDatabase + '.[dbo].[DIM_HIERARCHY] B
ON A.Hierarchy_Desc = B.Hierarchy_Desc
WHERE A.Hierarchy_SKey in (' + ##Harray + ');'
exec (##sql);
Declare ##config as NVARCHAR(MAX);
SELECT ##config = COALESCE(##config + ', H' + cast(A.[NEW] as nvarchar), 'H' + cast(A.[NEW] as nvarchar))
FROM ##TEMPHCONVERT A;
Print ##config
Which returns the value: "H15, H16, H17, H18"
When this is plugged into the dynamic SQL statement though I get the error...
Declare #SourceDatabase as nvarchar(10)
Declare #DestDatabase as nvarchar(10)
Declare ##sql as nvarchar(max) --variable to hold sql statements for this stored proc
Declare ##Harray as nvarchar(max) -- variable to hold hierarchy array elements from source
Set #SourceDatabase = 'D_EXP_CPM';
Set #DestDatabase = 'T_EXP_CPM';
Declare ##config as NVARCHAR(MAX);
set ##sql =
'SELECT
B.Hierarchy_SKey AS ''NEW'', A.Hierarchy_SKey AS ''OLD''
INTO ##TEMPHCONVERT
FROM ' + #SourceDatabase + '.[dbo].[DIM_HIERARCHY] A
INNER JOIN ' + #DestDatabase + '.[dbo].[DIM_HIERARCHY] B
ON A.Hierarchy_Desc = B.Hierarchy_Desc
WHERE A.Hierarchy_SKey in (' + ##Harray + ');'
exec (##sql);
set ##sql = '
UPDATE A SET A.[Value_Text] = (SELECT ##config = COALESCE(##config + '', H'' + cast(A.[NEW] as nvarchar), ''H'' + cast(A.[NEW] as nvarchar))
FROM ##TEMPHCONVERT A)
FROM ' + #DestDatabase + '.[dbo].[DIM_CONFIG] A ON A.[Config_Desc] = ''JBCODE FTE Map Hierarchy List'' ;'
exec (##sql);
Note I've cut quite a bit of code out of the middle here to make the post as short as possible. Can anybody explain why I'm getting the error?
I've tried declaring the variable inside the dynamic SQL statement in two places but neither allowed the code to run. I'm thinking maybe the variable needs passing somehow but I'm not sure how to do that through to the sub query.

Answer 1

Put the ##config Declaration in the ##sql string:
Declare #SourceDatabase as nvarchar(10)
Declare #DestDatabase as nvarchar(10)
Declare ##sql as nvarchar(max) --variable to hold sql statements for this stored proc
Declare ##Harray as nvarchar(max) -- variable to hold hierarchy array elements from source
Set #SourceDatabase = 'D_EXP_CPM';
Set #DestDatabase = 'T_EXP_CPM';
set ##sql =
'SELECT
B.Hierarchy_SKey AS ''NEW'', A.Hierarchy_SKey AS ''OLD''
INTO ##TEMPHCONVERT
FROM ' + #SourceDatabase + '.[dbo].[DIM_HIERARCHY] A
INNER JOIN ' + #DestDatabase + '.[dbo].[DIM_HIERARCHY] B
ON A.Hierarchy_Desc = B.Hierarchy_Desc
WHERE A.Hierarchy_SKey in (' + ##Harray + ');'
exec (##sql);
set ##sql = 'Declare ##config as NVARCHAR(MAX)
UPDATE A SET A.[Value_Text] = (SELECT COALESCE(##config + '', H'' + cast(A.[NEW] as nvarchar), ''H'' + cast(A.[NEW] as nvarchar))
FROM ##TEMPHCONVERT A)
FROM ' + #DestDatabase + '.[dbo].[DIM_CONFIG] A ON A.[Config_Desc] = ''JBCODE FTE Map Hierarchy List'' ;'
exec (##sql);

Answer 2

I'm not sure why you are getting the error, but this is a slight rewrite from what you have. Rather than concatenating a long string, I like to declare a template and then replace the parameters before executing. It just makes it more readable to me. I moved all of the related code into ##sql and just return the results in a temp table.
Declare ##sql as nvarchar(max);
Declare #SourceDatabase as nvarchar(10);
Declare #DestDatabase as nvarchar(10);
Declare ##Harray as nvarchar(max) ;
Set #SourceDatabase = 'D_EXP_CPM';
Set #DestDatabase = 'T_EXP_CPM';
set ##Harray = '1,2,3';
set ##sql = '
SELECT B.Hierarchy_SKey AS ''NEW'', A.Hierarchy_SKey AS ''OLD''
INTO #TEMPHCONVERT
FROM [[source]].[dbo].[DIM_HIERARCHY] A
INNER JOIN [[dest]].[dbo].[DIM_HIERARCHY] B
ON A.Hierarchy_Desc = B.Hierarchy_Desc
WHERE A.Hierarchy_SKey in ([Harray]);
Declare ##config as NVARCHAR(MAX);
SELECT ##config = COALESCE(##config + '', H'' + cast(A.[NEW] as nvarchar), ''H'' + cast(A.[NEW] as nvarchar))
FROM #TEMPHCONVERT A;
select [config] = ##config into ##config
'
set ##sql = replace(##sql, '[source]', #SourceDatabase)
set ##sql = replace(##sql, '[dest]', #DestDatabase)
set ##sql = replace(##sql, '[Harray]', ##Harray)
exec (##sql);
select * from ##config
drop table ##config

Answer 3

Declare #config as NVARCHAR(MAX);
SELECT #config = COALESCE(#config + ', H' + cast(A.[NEW] as nvarchar), 'H' + cast(A.[NEW] as nvarchar))
FROM #TEMPHCONVERT A;
set #sql = 'UPDATE A SET A.[Value_Text] = (#config )
FROM ' + #DestDatabase + '.[dbo].[DIM_CONFIG] A WHERE A.[Config_Desc] = ''JBCODE FTE Map Hierarchy List'' ;'
PRINT 'STEP 15 COMPLETE';