Postgre database-defined functions

Custom Functions

1, the query function:

     select prosrc from pg_proc where proname = 'test' test as a function name.

2, delete function:

     drop function test (anyelement, anyelement, numeric) test as a function name.

3, the definition of database functions: 

  create or replace function calculate_speed(end_time anyelement,begin_time anyelement,length numeric) RETURNS numeric  as
  $$
     declare
     total_second numeric;
     begin
            select extract(epoch from((end_time::timestamp - begin_time)))/3.6 into total_second;
            return round(length::numeric/total_second::numeric,3);
     end;
  $$ LANGUAGE plpgsql;