Dine kolonner er af datatypen TIMESTAMP, som denne:
SQL> create table mytable (start_time,end_time)
2 as
3 select to_timestamp('2009-05-01 12:34:56','yyyy-mm-dd hh24:mi:ss')
4 , to_timestamp('2009-05-01 23:45:01','yyyy-mm-dd hh24:mi:ss')
5 from dual
6 union all
7 select to_timestamp('2009-05-01 23:45:01','yyyy-mm-dd hh24:mi:ss')
8 , to_timestamp('2009-05-02 01:23:45','yyyy-mm-dd hh24:mi:ss')
9 from dual
10 union all
11 select to_timestamp('2009-05-01 07:00:00','yyyy-mm-dd hh24:mi:ss')
12 , to_timestamp('2009-05-01 08:00:00','yyyy-mm-dd hh24:mi:ss')
13 from dual
14 /
Tabel is aangemaakt.
At trække et tidsstempel fra et andet fører til en INTERVAL-datatype:
SQL> select start_time
2 , end_time
3 , end_time - start_time time_difference
4 from mytable
5 /
START_TIME END_TIME TIME_DIFFERENCE
------------------------------ ------------------------------ ------------------------------
01-05-09 12:34:56,000000000 01-05-09 23:45:01,000000000 +000000000 11:10:05.000000000
01-05-09 23:45:01,000000000 02-05-09 01:23:45,000000000 +000000000 01:38:44.000000000
01-05-09 07:00:00,000000000 01-05-09 08:00:00,000000000 +000000000 01:00:00.000000000
3 rijen zijn geselecteerd.
Og INTERVAL-datatyper kan ikke summeres. Det er en irriterende begrænsning:
SQL> select sum(end_time - start_time)
2 from mytable
3 /
select sum(end_time - start_time)
*
FOUT in regel 1:
.ORA-00932: inconsistente gegevenstypen: NUMBER verwacht, INTERVAL DAY TO SECOND gekregen
For at omgå denne begrænsning kan du konvertere og beregne med antallet af sekunder, sådan her:
SQL> select start_time
2 , end_time
3 , trunc(end_time) - trunc(start_time) days_difference
4 , to_number(to_char(end_time,'sssss')) - to_number(to_char(start_time,'sssss')) seconds_difference
5 from mytable
6 /
START_TIME END_TIME DAYS_DIFFERENCE SECONDS_DIFFERENCE
------------------------------ ------------------------------ --------------- ------------------
01-05-09 12:34:56,000000000 01-05-09 23:45:01,000000000 0 40205
01-05-09 23:45:01,000000000 02-05-09 01:23:45,000000000 1 -80476
01-05-09 07:00:00,000000000 01-05-09 08:00:00,000000000 0 3600
3 rijen zijn geselecteerd.
Og så er det normale TAL, der kan summeres
SQL> select sum
2 ( 86400 * (trunc(end_time) - trunc(start_time))
3 + to_number(to_char(end_time,'sssss')) - to_number(to_char(start_time,'sssss'))
4 ) total_time_difference
5 from mytable
6 /
TOTAL_TIME_DIFFERENCE
---------------------
49729
1 rij is geselecteerd.
Og hvis du ønsker det, kan du konvertere dette tal tilbage til et INTERVAL:
SQL> select numtodsinterval
2 ( sum
3 ( 86400 * (trunc(end_time) - trunc(start_time))
4 + to_number(to_char(end_time,'sssss')) - to_number(to_char(start_time,'sssss'))
5 )
6 , 'second'
7 ) time_difference
8 from mytable
9 /
TIME_DIFFERENCE
------------------------------
+000000000 13:48:49.000000000
1 rij is geselecteerd.
Med venlig hilsen Rob.