Different SRID shown in QGIS and PostGIS for the same data

Question

I have data stored in PostGIS. When I view its properties in QGIS, it says:

SRS: EPSG:4326 - WGS 84

However, when I want retrieve the SRID value directly using the Find_SRID function, it returns 0. And by looking at the data, SRID is really 0 in PostGIS.

Query:

select * from geometry_columns;

Returns:

f_table_name | f_geometry_column | coord_dimension | srid |  type

-----------------+------------------+--------------+-------------------

vector       | wkb_geometry      |               2 |    0 | POINT

vector       | wkb_geometry      |               2 |    0 | POINT

buff_out     | wkb_geometry      |               2 |    0 | POLYGON

buff_out     | wkb_geometry      |               2 |    0 | POLYGON

Question: Why is SRID for the same data different in QGIS and in PostGIS? How do I get the correct SRID value from PostGIS?

I am using PostGIS 9.5.

Answer 1

You could try the following (as an example) if you still have issues.

SELECT UpdateGeometrySRID('vector','wkb_geometry',4326);

In QGIS when you add layers to canvas you only set the SRID for that proyect's layers

Answer 2

To update the SRID in PostgreSQL/PostGIS you can run:

ALTER TABLE vector ALTER COLUMN wkb_geometry TYPE geometry(POINT,4326) using ST_SetSRID(wkb_geometry, 4326);

This does the exact same thing as YPCA's answer, but is standard SQL.