How to find closest point on multi line String from a point in PostGIS

Question

I want to find out the nearest point on my road network which is a multiline string from a point with lat lon value. I have tried the following codes but it giving a error message that my road network is not a line.

SELECT ST_AsText(ST_Line_Interpolate_Point(foo.the_line, ST_Line_Locate_Point(foo.the_line, ST_GeomFromText('POINT(90.402 23.752)'))))
FROM (SELECT ST_GeomFromText(geom) As the_line from roads) As foo;

Where geom is my geometry column with multiLineString
roads is the table name
Long 90.402 and Lat 23.752
Projected Coordinate system UTM_Zone_46N

Answer 1

How about just using ST_ClosestPoint?

SELECT ST_AsText(ST_ClosestPoint(
    ST_GeomFromText('MULTILINESTRING ((10 10, 40 50), (20 20, 50 20, 50 60, 20 20))'),
    ST_GeomFromText('POINT(20 40)')
));

http://postgis.net/docs/manual-1.5/ST_ClosestPoint.html

Answer 2

To my knowledge you cant. MULTILINESTRING does not quarantee that your LINE is collection of continous LINES. Your query works if you can change your multilines to linestrings ( you can use ST_LineMerge())