The unique ID of an t_xlink entry is stored as a BIGINT value (INTEGER for SQLite).

This BIGINT value (INTEGER for SQLite) points to the ID of the link in the table t_link.

This is the ID of the database item that the note is linked to, stored as a BIGINT value (INTEGER for SQLite).

This field stores the type of the link (URL, PDF, fulltext, related, or image).

This field stores whether the link is used in a reference or in a note.