You might encounter the below error while trying to modify a column in Redshift database from SQL Workbench.
[Amazon](500310) Invalid operation: ALTER TABLE ALTER COLUMN cannot run inside a transaction block; 1 statement failed.
You can overcome this error by turning Autocommit ON before running the alter table statement. You may later turn the Autocommint OFF after modifying the column.
Example:
set autocommit on; alter table schemaname.tablename alter column columnname type varchar(2000); set autocommit off;