Set a cursor on a table inside a table variable - sql

Question

All,
Trying to set a cursor on a table value inside a table variable, but it does not work. can anyone comment on how I can fix this?
** the code below is called from another stored procedure which provides the value for the tablename variable **
ALTER PROCEDURE [dbo].[usrSetLTDNormDist]
-- Add the parameters for the stored procedure here
#TableName Sysname,
---...
DECLARE #SQLCommand1 NVARCHAR(MAX) = N'
Set #RecCursor1 = Cursor For
Select [Volume], [TRANSDATE] from #TableName'
EXECUTE dbo.sp_executesql #sqlCommand1
-- Open Cursor
Open #RecCursor1
Fetch Next From #RecCursor1
Into #Volume, #TransDate
---...

Answer 1

Add PRINT #SQLCommand1 between the DECLARE and EXECUTE statements to review what is actually being executed. Based on your code snippet, you will see
Set #RecCursor1 = Cursor For
Select [Volume], [TRANSDATE] from #TableName
...that is, the value you set in #TableName is not automagically added to the script. Here's the way I write these things:
DECLARE #SQLCommand1 NVARCHAR(MAX)
SET #SQLCommand1 = replace(N'
Set #RecCursor1 = Cursor For
Select [Volume], [TRANSDATE] from <#TableName>'
,'<#TableName>', #TableName)
PRINT #SQLCommand1
EXECUTE dbo.sp_executesql #sqlCommand1
I use the < > characters to make the replaced values stand out.

Answer 2

This script demonstrates the general technique:
create table T (ID int not null)
go
insert into T(ID) values (99)
go
declare #TableName sysname
declare #ID int
set #TableName = 'T'
declare #SQL nvarchar(max) = N'declare boris cursor for select ID from ' +
QUOTENAME(#TableName)
exec sp_executesql #SQL
open boris
fetch next from boris into #ID
while ##FETCH_STATUS = 0
begin
print #ID
fetch next from boris into #ID
end
close boris
deallocate boris
Producing this output:
(1 row(s) affected)
99
However, I will offer my usual caution - if you're in a situation where you want to operate against multiple tables in the same way, this is usually a sign of a broken data model. Usually there ought to be a single table with additional columns containing data that serves to differentiate the values.