PostgreSQL计算浮点坐标和geom之间的距离（以米为单位）

Question

I have to queries, one tries to calculate the distance between floats coordinates (x1,y1,x2,y2), and the other tries to calculate the distance between a geom and an float coordinate, both should return distance in meters.

I'm using the following query for the 2 floats:

ST_Distance_Sphere(st_setsrid(st_makepoint(longitude, latitude),4326), st_setsrid(st_makepoint(?,?),4326)) AS distance

And The querty for geom and float is:

ST_Distance_Sphere(geom, st_setsrid(st_makepoint(?,?),4326)) AS distance

I can't to fully understand the SRID concept, and I'm having the feeling that my numbers are incorrects because of it.

Can someone help to output a distance in meters?

Thanks, Itay.