ORACLE inquiry nearly a day, the data within half an hour

SELECT fields FROM table WHERE time field BETWEEN SYSDATE-1 AND SYSDATE; // query data within a day

 

sysdate + 1 plus one day
sysdate + 1/24 was added 1 hour
sysdate + 1 / (24 * 60 ) plus one minute
sysdate + 1 / (24 * 60 * 60) plus 1 sec

Save sysdate-1 one day
sysdate-1/24 minus 1 hour
sysdate-1 / (24 * 60 ) minus one minute
sysdate-1 / (24 * 60 * 60) minus 1 second
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SELECT FROM table WHERE field time field BETWEEN ADD_MONTHS (SYSDATE, -1) AND SYSDATE; // query data a month ago

 

ADD_MONTHS (SYSDATE, -1) minus one month

ADD_MONTHS (SYSDATE, 1) plus one month