# example of reading regular data table from Postgres using RPostgresSQL library
library(RPostgreSQL)
con <- dbConnect(PostgreSQL(), host="localhost", port="5432", user="username", password="password", dbname="db_name")
result <- dbGetQuery(con, statement = "SELECT * FROM table1, table2 WHERE table1.key = table2.key")
head(result)

library(rpostgis)
conn <- dbConnect(PostgreSQL(), host="localhost", port="5432", user="postgres", password="postgres", dbname="sp_db")
dbSchema(conn, name = 'sp_db')
dbTableInfo(conn, "sp_table")
my_spdf<-pgGetGeom(conn, name="sp_table", geom = "wkb_geometry")
head(my_spdf@data)