taken from: https://github.com/jmoiron/sqlx/issues/255 DBFields reflects on a struct and returns the values of fields with `db` tags and returns the keys.

DBValues reflects on a struct and returns the values of fields which have a `db` tag.

DBPlaceholder reflects on a struct and returns a placeholder string for every field which have a `db` tag.

DBValues reflects on a struct and returns the values of fields which have a `db` tag.