Online Trick

QspatiaLite Use Case: Connecting Lines

With QSpatiaLIte you can connect disjoint lines quite easily. With the below SQL you can allow for a grouping variable, in this case the field 'name' within the layer 'segments', by which the group vertices are collected and connected as lines! With this approach the vertices are connected in the order in which they were digitized and existing gaps are closed.

select 
  name as name,
  makeLine(t.ptgeom, 0) as geom 
from (
     select
        name as name,
        DissolvePoints(Collect(ST_Reverse(geometry)))  as ptgeom
     from segments group by name )
as t