Query failed: ERROR: Operation on two geometries with different SRID

Question

Following the pgRouting workshop here, I have the routing query below:

$sql = "SELECT gid, start_id AS source, end_id AS target, the_geom, 
                  distance(the_geom, GeometryFromText(
                       'POINT(".$lonlat[0]." ".$lonlat[1].")', 4326)) AS dist 
                 FROM ".TABLE."  
                 WHERE the_geom && setsrid(
                       'BOX3D(".($lonlat[0]-0.1)." 
                              ".($lonlat[1]-0.1).", 
                              ".($lonlat[0]+0.1)." 
                              ".($lonlat[1]+0.1).")'::box3d, 4326) 
                 ORDER BY dist LIMIT 1";

This query fails with the error: Query failed: ERROR: Operation on two geometries with different SRIDs. Now, I've been looking around and came across this. I've tried the suggestions on this post, but the error persists. Any idea on how to fix this will be appreciated.

UPDATE: Running SELECT st_srid(the_geom) FROM table_name against my database table returns -1. In my query and map, the assumed external projection is EPSG:4326. Is changing this value likely to help? Is there any harm in changing the srid value directly in the database? How can I go about changing the srid value in the database if it doesn't present any risk?

UPDATE: I had to change the srid of the column from the UNKNOWN indicator of -1 to 4326. The answer at this StackOverflow post was very helpful in this. Also, the question in this SE GIS post was instrumental in helping me in the right direction.

Answer 1

I had to change the srid of the column from the UNKNOWN indicator of -1 to 4326. The answer at this StackOverflow post was very helpful in this. Also, the question in this SE GIS post was instrumental in helping me in the right direction.

Summarily: Running UPDATE table_name SET the_geom = ST_SetSRID(the_geom, 4326) and UPDATE table_name SET the_geom = ST_Transform(the_geom, 4326) did it.

Answer 2

There's an error in okello's answer: the two commands should be in inverted order. It's UPDATE table_name SET the_geom = ST_Transform(the_geom, 4326) first, to do the conversion, and then UPDATE table_name SET the_geom = ST_SetSRID(the_geom, 4326) to tell PostGIS that the new values are to be interpreted as WGS84.