The usual way to delete a function – any entity, for that matter, is

delete entity from namespace


delete foo from `.

However, .z is a special namespace, so delete doesn’t work:

q).z.ts: {47}
q)delete ts from `.z

There is a special command just for removing elements from .z:

q)\x .z.pi

See \x (expunge).

The delete command works for that, too. To remove a column named xyz from table t, use

delete xyz from `t // in place delete (backquote)
delete xyz from t  // returns a copy minus column xyz

Use delete and the virtual column i:

delete from `t where i = n

Don’t forget the backquote if you intend to delete-in-place.