I would like to add comments to all of our columns, programmatically. The only way I can find to do this is through SQL DDL - e.g. `alter table sometable alter column somecolumn comment 'some comment string`. However, I want to read this comment string from a YAML file, and protect against SQL injection. I cannot find a way to do this - if I use `alter table sometable alter column somecolumn comment :placeholder` I get a syntax error on the colon.

I know that e.g. special characters like single quotes work in comments, because I can edit and apply them manually - but it's not obvious how to do this with DDL when updating a table programmatically.