SQL Server - script to update database columns from varchar to nvarchar if not already nvarchar

Question

I am in a situation where I must update an existing database structure from varchar to nvarchar using a script. Since this script is run everytime a configuration applicati

Answer 1

The issue with Josef's answer is that it would change NOT NULL fields to NULL after executing the queries. The following manipulation fixes it:

SELECT cmd = 'alter table [' + c.table_schema + '].[' + c.table_name 
 + '] alter column [' + c.column_name + '] nvarchar('
 +CASE WHEN CHARACTER_MAXIMUM_LENGTH<=4000
       THEN CAST(CHARACTER_MAXIMUM_LENGTH as varchar(10)) ELSE 'max' END+')' 
 + CASE WHEN IS_NULLABLE='NO' THEN ' NOT NULL' ELSE '' END,*
FROM information_schema.columns c
WHERE c.data_type='varchar' 
ORDER BY CHARACTER_MAXIMUM_LENGTH desc

Credits to Igor's answer