postgis - How to export geometry as a table in QGIS

I am trying to use Qgis to produce the input file for SWMM and the first step is to produce the geometry tables. I need to export the geometry of elements as a tables with these format:

(poygons)

;;Subcatchment   X-Coord            Y-Coord           

;;-------------- ------------------ ------------------
Area1            134880.644         6495607.728       
Area1            135200.867         6495595.252       
Area1            134859.850         6495577.785       
Area1            134864.009         6495608.560       
Area2            135202.531         6495594.420       
Area2            135117.692         6495685.081       
Area2            134870.663         6495665.119       
Area2            134863.177         6495608.560       

(lines)

;;Link           X-Coord            Y-Coord           
;;-------------- ------------------ ------------------
Link3            134941.633         6495830.023       
Link3            134953.814         6495860.476       

(points)

;;Node           X-Coord            Y-Coord           
;;-------------- ------------------ ------------------
Node1            134866.732         6495657.169       

Node2            134918.668         6495651.752       
Node3            134919.624         6495674.375       
Node4            134933.644         6495678.517       
Node5            135002.538         6495870.626       
Outfall1         134890.879         6496098.005       

So far, I have tried the MMQIS, but I do not know how to tailor the output:

"shapeid","x","y"
"0","134956.853261","6495850.73098"
"0","134951.891304","6495838.10054"

"0","134944.222826","6495660.82337"
"0","135027.44837","6495695.78261"
"0","135001.223092","6495794.37799"
"0","135013.690217","6495854.33967"
"0","135010.081522","6495867.4212"
"0","134956.853261","6495850.73098"

My guess is that a set of SQL sentences could do the work (I saw https://gis.stackexchange.com/a/10113/36393), but I have no clue how to start them and what I need.

The elements are stored in separate files (GeoPackage or shape), I do not care about the attribute table (now) and I think I will be able to use a database. I have PostGIS (I am very unexperienced on it), but maybe it is easier to work with a SpatiaLite file.

Answer

It´s a bit puzzling to me why any software would require a fixed space delimited format as input...but anyway, AFAIK within QGIS your options are limited since both 'Save as...' -> CSV and the MMQGIS have their backdraws for your requirements.

PostgreSQL's COPY (or /copy if your DB rights are limited) does give you more flexibility in constructing the table structure, albeit still with no fixed space delimiter:

COPY (
    SELECT concat('Area', sub.id::text) AS "Subcatchment",
           ST_X(sub.geom) AS "X-Coord",
           ST_Y(sub.geom) AS "Y-Coord"
    FROM (
        SELECT ROW_NUMBER() OVER() AS id,
               (ST_DumpPoints(geom)).geom AS geom
        FROM 
    ) AS sub

) TO 'path/to/file.csv' DELIMITER ' ' CSV HEADER;

This is the example query for your area table, for the lines just replace 'Subcatchment' and 'Area' with 'Link' and refer to your line table ( in above query).

For your Points, use:

COPY (
    SELECT concat('Node', sub.id::text) AS "Node",
           ST_X(sub.geom) AS "X-Coord",
           ST_Y(sub.geom) AS "Y-Coord"
    FROM (
        SELECT ROW_NUMBER() OVER() AS id,
               geom

        FROM 
    ) AS sub
) TO 'path/to/file.csv' DELIMITER ' ' CSV HEADER;

This gives you a CSV each, delimited by one space and without quotes (this is dependant on a few things, but should be true for your case). Note that your geometry column is called the kind-of standard 'geom' in above queries, so name yours accordingly.