def migrate_varchar_to_nvarchar():

    if dbdriver != "sqlserver2005":

        return

    introspection_sql = """\

SELECT table_schema, table_name, column_name, is_nullable, character_maximum_length

FROM information_schema.columns

WHERE data_type = 'VARCHAR' and table_name <> 'SYSDIAGRAMS'

"""

    has_index_sql = """\

SELECT i.name AS index_name,

       i.type_desc,

       i.is_unique,

       i.is_unique_constraint

FROM sys.indexes AS i, sys.index_columns as j, sys.columns as k

WHERE is_hypothetical = 0 AND i.index_id <> 0

AND i.object_id = j.object_id

AND i.index_id = j.index_id

AND i.object_id = OBJECT_ID('%(table)s')

AND k.name = '%(col)s'

AND k.object_id=i.object_id

AND j.column_id = k.column_id;"""

    generated_statements = []

    for schema, table, column, is_nullable, length in sql(introspection_sql, ask_confirm=False):

        qualified_table = '[%s].[%s]' % (schema, table)

        rset = sql(has_index_sql % {'table': qualified_table, 'col':column},

                   ask_confirm = False)

        drops = []

        creates = []

        for idx_name, idx_type, idx_unique, is_unique_constraint in rset:

            if is_unique_constraint:

                drops.append('ALTER TABLE %s DROP CONSTRAINT %s' % (qualified_table, idx_name))

                creates.append('ALTER TABLE %s ADD CONSTRAINT %s UNIQUE (%s)' % (qualified_table, idx_name, column))

            else:

                drops.append('DROP INDEX %s ON %s' % (idx_name, qualified_table))

                if idx_unique:

                    unique = 'UNIQUE'

                else:

                    unique = ''

                creates.append('CREATE %s %s INDEX %s ON %s(%s)' % (unique, idx_type, idx_name, qualified_table, column))

        if length == -1:

            length = 'max'

        if is_nullable == 'YES':

            not_null = 'NULL'

        else:

            not_null = 'NOT NULL'

        alter_sql = 'ALTER TABLE %s ALTER COLUMN %s NVARCHAR(%s) %s' % (qualified_table, column, length, not_null)

        generated_statements+= drops + [alter_sql] + creates

    for statement in generated_statements:

        print statement

        sql(statement, ask_confirm=False)

    commit()

migrate_varchar_to_nvarchar()