Postgres 12

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CREATE TABLE t (geom geometry(point,4326));

CREATE TABLE

SELECT Find_SRID('public','t','geom'); 

find_srid

4326

SELECT 1

INSERT INTO t VALUES ('SRID=4326;POINT(1 42)'::geometry);

INSERT 0 1

SELECT ST_SRID(geom) FROM t; 

st_srid

4326

SELECT 1

SELECT ST_SRID('POINT(1 42)'::geometry);

st_srid

0

SELECT 1