Problem With Dynamic Queries In SQL Tasks

Hello, i have dynamic queries for example:

DECLARE @query nvarchar(250);
DECLARE @table nvarchar(100);
SET @table = 'table_name';

SET @query=
N'update '+@table+'
set column = 0
where column is null';
EXECUTE sp_executesql @query

SET @query=
N'update '+@table+'
set column2 = 0
where column2 is null';
EXECUTE sp_executesql @query

It is very simple example. My question is: it is possible somehow put these queries in SQL Tasks?
Because if i do like this i get error "The Declare cursor SQL construct or statement is not supported."
Maybe there is other way to solve my problem? Or maybe syntax should be changed?
Thanks for advice