sqlutil: new operator to allow transparent datetime truncation across various DBMS

[pvanek]

Missing functionality like this (for Oracle):

alter session set nls_date_format = 'dd.mm.yyyy hh24:mi:ss';

select
      trunc(sysdate, 'MI')
    , trunc(sysdate, 'HH24')
    , trunc(sysdate, 'DD')
    , trunc(sysdate, 'MM')
    , trunc(sysdate, 'YYYY')
  from dual;

"TRUNC(SYSDATE,'MI')"	"TRUNC(SYSDATE,'HH24')"	"TRUNC(SYSDATE,'DD')"	"TRUNC(SYSDATE,'MM')"	"TRUNC(SYSDATE,'YYYY')"
03.08.2017 10:38:00	03.08.2017 10:00:00	03.08.2017 00:00:00	01.08.2017 00:00:00	01.01.2017 00:00:00

Analogies for:

mysql:

CAST(DATE_FORMAT(tstamp,'%Y-%m-%d %H:%i:00') AS DATETIME)

pgsql:

date_trunc('hour', current_timestamp)