How can I return all the rows in a PostgreSQL/PostGIS table within a radius of Xkm provided by a longitude and latitude value? - sql

Question

I'm trying to have a go at learning about PostgreSQL and in particular, it's PostGIS extension and the benefits with regards to geographic spatial features it provides. I've loaded a PostgreSQL DB with a table that contains 30,000 records of latitude, longitude and a price value (for houses) and I want to start querying the DB to return all the rows that would be in a radius of Xkm of a particular latitude and longitude.
I've hit a brick wall as to how I might run this type of query as I've found the documentation to be quite limited online and I've found no similar attempts at this method of querying online.
Some methods I've tried:
SELECT *
FROM house_prices
WHERE ST_DWithin( ST_MakePoint(53.3348279,-6.269547099999954)) <= radius_mi *
1609.34;
This prompts the following error:
ERROR: function st_dwithin(geometry) does not exist
Another attempt:
SELECT * FROM house_prices ST_DWithin( 53.3348279, -6.269547099999954, 5); <-- A latitude value, longitude value and 5 miles radius
This prompts the following error:
ERROR: syntax error at or near "53.3348279"
Could anyone point me in the right direction/ know of some documentation I could look at?
** Edit **
Structure and set up of database and table in pgAdmin4

Answer 1

The first query has an invalid number of parameters. The function ST_DWithin expects at least two geometries and the srid distance,
and optionally a Boolean parameter indicating the usage of a spheroid (see documentation).
The second query is missing a WHERE clause and has the same problem as the first query.
Example from documentation:
SELECT s.gid, s.school_name
FROM schools s
LEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.the_geom, 3000)
WHERE h.gid IS NULL;
Perhaps something like this would be what you want to achieve:
SELECT *
FROM house_prices h
WHERE ST_DWithin(ST_MakePoint(53.3348,-6.2695),h.geom,h.radius_mi * 1609.34)
Also pay attention to the order of the coordinates pair (x,y or y,x), otherwise you might easily land on the sea with these coordinates ;-)
EDIT： Taking into account that there is no geometry on the table, so the points are stored in two different columns, longitude and latitude:
SELECT *
FROM house_prices
WHERE ST_DWithin(ST_MakePoint(longitude,latitude),ST_MakePoint(53.3348,-6.2695),1609.34)